Stoichiometry and Thermochemistry MCQ Practice with Answers

Posted on Aug 26, 2024 in Chemistry

Topic 1: Stoichiometry

Questions and Answers

1. What amount of oxygen, O₂, (in moles) contains 1.8×10²² molecules?

B. 0.030

2. Which compound has the empirical formula with the greatest mass?

B. C₄H₁₀

3. C₂H₂(g) + O₂(g) → CO₂(g) + H₂O(g)

When the equation above is balanced, what is the coefficient for oxygen?

D. 5

4. 3.0 dm³ of sulfur dioxide is reacted with 2.0 dm³ of oxygen according to the equation below.

2SO₂(g) + O₂(g) → 2SO₃(g)

What volume of sulfur trioxide (in dm³) is formed? (Assume the reaction goes to completion and all gases are measured at the same temperature and pressure.)

C. 3.0

5. What will happen to the volume of a fixed mass of gas when its pressure and temperature (in Kelvin) are both doubled?

A. It will not change.

6. What amount (in moles) is present in 2.0 g of sodium hydroxide, NaOH?

A. 0.050

7. A hydrocarbon contains 90% by mass of carbon. What is its empirical formula?

B. C₃H₄

8. Copper can react with nitric acid as follows.

3Cu +_HNO₃  _Cu(NO₃)₂ +_H₂O + _NO

What is the coefficient for HNO₃ when the equation is balanced?

C. 8

9. Lithium hydroxide reacts with carbon dioxide as follows.

2LiOH + CO₂ → Li₂CO₃ + H₂O

What mass (in grams) of lithium hydroxide is needed to react with 11 g of carbon dioxide?

B. 12

10. Which change in conditions would increase the volume of a fixed mass of gas?

	Pressure /kPa	Temperature /K
D	Halved	Double

11. How many hydrogen atoms are contained in one mole of ethanol, C₂H₅OH?

D. 3.6×10²⁴

12. The percentage by mass of the elements in a compound is C = 72%, H = 12%, O = 16%. What is the mole ratio of C:H in the empirical formula of this compound?

B. 1 : 2

13. What is the coefficient for O₂(g) when the equation below is balanced?

__C₃H₈(g) + __O₂(g) → __CO₂(g) + __H₂O(g)

C. 5

14. What amount of NaCl (in moles) is required to prepare 250 cm³ of a 0.200 mol dm^–3 solution?

D. 0.0500

15. For which set of conditions does a fixed mass of an ideal gas have the greatest volume?

	Temperature	Pressure
D.	High	Low

16. Which of the following contains the greatest number of molecules?

A. 1 g of CH₃Cl

17. Which of the following compounds has/have the empirical formula CH₂O?

I. CH₃COOH

II. C₆H₁₂O₆

III. C₁₂H₂₂O₁₁

C. I and II only

18. Assuming complete reaction, what volume of 0.200 mol dm^–3 HCl(aq) is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 Ba(OH)₂(aq)?

C. 50.0 cm³

19. Under what conditions would one mole of methane gas, CH₄, occupy the smallest volume?

B. 273 K and 2.02×10⁵ Pa

20. The temperature in Kelvin of 2.0 dm³ of an ideal gas is doubled and its pressure is increased by a factor of four. What is the final volume of the gas?

A. 1.0 dm³

21. Which is a correct definition of the term empirical formula?

D. Formula showing the simplest ratio of numbers of atoms of each element in a compound

22. The reaction of ethanal and oxygen can be represented by the unbalanced equation below.

__ CH₃CHO + __ O₂ → __ CO₂ + __ H₂O

When the equation is balanced using the smallest possible integers, what is the coefficient for O₂?

C. 5

23. The equation for the complete combustion of butane is

2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O

What is the amount (in mol) of carbon dioxide formed by the complete combustion of three moles of butane?

C. 12

24. Which solution contains the greatest amount (in mol) of solute?

C. 30.0 cm³ of 0.300 mol dm^–3 NaCl

25. A fixed mass of an ideal gas has a volume of 800 cm³ under certain conditions. The pressure (in kPa) and temperature (in K) are both doubled. What is the volume of the gas after these changes with other conditions remaining the same?

B. 800 cm³

26. The complete oxidation of propane produces carbon dioxide and water as shown below.

C₃H₈ + __O₂ __CO₂ + __H₂O

What is the total of the coefficients for the products in the balanced equation for 1 mole of propane?

B. 7

27. The relative molecular mass (M_r) of a compound is 60. Which formulas are possible for this compound?

I. CH₃CH₂CH₂NH₂

II. CH₃CH₂CH₂OH

III. CH₃CH(OH)CH₃

C. II and III only

28. Which sample has the least number of atoms?

A. 1 mol of H₂SO₄

29. Avogadro’s constant has the same value as the number of

A. Molecules in 1 mol of solid iodine.

30. What is the total of all the coefficients in the balanced equation for the reduction of 1 mol of MnO₄^–?

__ MnO₄^– +__H⁺ + __ e^– __Mn²⁺ + __H₂O

D. 19

31. Which contains the same number of ions as the value of Avogadro’s constant?

A. 0.5 mol NaCl

32. A reaction occurring in the extraction of lead from its ore can be represented by this unbalanced equation:

__ PbS + __O₂  __ PbO + __ SO₂

When the equation is balanced using the smallest possible whole numbers, what is the coefficient for O₂?

C. 3

33. The equation for a reaction occurring in the synthesis of methanol is

CO₂ + 3H₂  CH₃OH + H₂O

What is the maximum amount of methanol that can be formed from 2 mol of carbon dioxide and 3 mol of hydrogen?

A. 1 mol

34. Which solution contains 0.1 mol of sodium hydroxide?

C. 100 cm³ of 1.0 mol dm^–3 NaOH

35. A cylinder of gas is at a pressure of 40 kPa. The volume and temperature (in K) are both doubled. What is the pressure of the gas after these changes?

C. 40 kPa

36. Which of the following quantities has units?

C. Molar mass

37. The empirical formula of a compound is C₂H₄O. Which molecular formulas are possible for this compound?

I. CH₃COOH

II. CH₃CH₂CH₂COOH

III. CH₃COOCH₂CH₃

C. II and III only

38. Calcium carbonate decomposes on heating as shown below.

CaCO₃  CaO + CO₂

When 50 g of calcium carbonate are decomposed, 7 g of calcium oxide are formed. What is the percentage yield of calcium oxide?

B. 25%

39. Sodium reacts with water as shown below.

__ Na + __ H₂O  __ NaOH + __ H₂

What is the total of all the coefficients when the equation is balanced using the smallest possible whole numbers?

D. 7

40. What is the total number of ions present in the formula, Al₂(SO₄)₃?

C. 5

41. A 4 g sample of sodium hydroxide, NaOH, is dissolved in water and made up to 500 cm³ of aqueous solution. What is the concentration of the resulting solution?

B. 0.2 mol dm^–3

42. Methane, CH₄, burns in oxygen gas to form carbon dioxide and water. How many moles of carbon dioxide will be formed from 8.0 g of methane?

B. 0.50

43. What is the empirical formula of a compound containing 50% by mass of element X (A_r = 20) and 50% by mass of element Y (A_r = 25)?

D. X₅Y₄

44. Assuming complete reaction, what volume of 0.200 mol dm^–3 potassium hydroxide solution (KOH(aq)), is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 aqueous sulfuric acid, (H₂SO₄(aq))?

C. 50.0 cm³

45. Consider the following reaction.

N₂(g) + 3H₂(g) 2NH₃(g)

If the reaction is made to go to completion, what volume of ammonia (in dm³) can be prepared from 25 dm³ of nitrogen and 60 dm³ of hydrogen? All volumes are measured at the same temperature and pressure.

A. 40

46. The temperature in Kelvin of 1.0 dm³ of an ideal gas is doubled and its pressure is tripled. What is the final volume of the gas in dm³?

A. 1.0 dm³

47. On complete combustion, a sample of a hydrocarbon compound produces 1.5 mol of carbon dioxide and 2.0 mol of water. What is the molecular formula of this hydrocarbon?

D. C₃H₈

48. When excess BaCl₂(aq) was added to a sample of Fe(NH₄)₂(SO₄)₂(aq) to determine the amount in moles of sulfate present, 5.02×10^–3 mol of BaSO₄ was obtained. How many moles of sulfate ions and iron ions were in the sample of Fe(NH₄)₂(SO₄)₂?

	Amount of sulfate ions / moles	Amount of iron ions / moles
A.	5.02×10^–3	2.51×10^–3

49. What volume of 0.500 mol dm^–3 sulfuric acid solution is required to react completely with 10.0 g of calcium carbonate according to the equation below?

CaCO₃(s) + H₂SO₄(aq)  CaSO₄(aq) + H₂O(l) + CO₂(g)

B. 200 cm³

50. Which expression gives the amount (in mol) of a substance, if the mass is given in grams?

51. What is the total number of atoms in 0.20 mol of propanone, CH₃COCH₃?

C. 1.2×10²⁴

52. When the equation below is balanced for 1 mol of C₃H₄, what is the coefficient for O₂?

C₃C₄ + O₂  CO₂ + H₂O

C. 4

53. Ethyne, C₂H₂, reacts with oxygen according to the equation below. What volume of oxygen (in dm³) reacts with 0.40 dm³ of C₂H₂?

2C₂H₂(g) + 5O₂(g)  4CO₂(g) + 2H₂O(g)

C. 1.0

54. Ethyne, C₂H₂, reacts with oxygen according to the equation below. What volume of oxygen (in dm³) reacts with 0.40 dm³ of C₂H₂?

2C₂H₂(g) + 5O₂(g)  4CO₂(g) + 2H₂O(g)

C. 1.0

55. What is the coefficient for H⁺ when the redox equation below is balanced?

Ag(s) + NO₃^–(aq) +H⁺(aq)  Ag⁺(aq) + NO(g) + H₂O(l)

D. 4

56. How many hydrogen atoms are in one mole of ethanol, C₂H₅OH?

B. 3.61×10²⁴

57. What is the coefficient for H₂SO₄(aq) when the following equation is balanced, using the smallest possible integers?

__Mg₃N₂(s) + __H₂SO₄(aq) → __MgSO₄(aq) + __(NH₄)₂SO₄(aq)

C. 4

58. Air bags in cars inflate when sodium azide decomposes to form sodium and nitrogen:

2NaN₃(s) → 2Na(s) + 3N₂(g)

Calculate the amount, in moles, of nitrogen gas produced by the decomposition of 2.52 mol of NaN₃(s).

C. 3.78

59. What volume, in cm³, of 0.200 mol dm^–3 HCl(aq) is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 Ba(OH)₂(aq)?

C. 50.0

Topic 5: Thermochemistry

Questions

1.

D. Energy is released when bonds are formed and absorbed when they are broken.

2. The temperature of a 2.0 g sample of aluminium increases from 25°C to 30°C. How many joules of heat energy were added? (Specific heat of Al = 0.90 J g^–1K^–1)

C. 9.0

3. Using the equations below:

C(s) + O₂(g) → CO₂(g) ∆H = –390 kJ
Mn(s) + O₂(g) → MnO₂(s) ∆H = –520 kJ

what is ∆H (in kJ) for the following reaction?

MnO₂(s) + C(s)  Mn(s) + CO₂(g)

B. 130

4. Which statements about exothermic reactions are correct?

I. They have negative H values.

II. The products have a lower enthalpy than the reactants.

III. The products are more energetically stable than the reactants.

D. I, II and III

5. A sample of a metal is heated. Which of the following are needed to calculate the heat absorbed by the sample?

I. The mass of the sample

II. The density of the sample

III. The specific heat capacity of the sample

B. I and III only

6. The average bond enthalpies for O—O and O==O are 146 and 496 kJ mol^–1 respectively. What is the enthalpy change, in kJ, for the reaction below?

H—O—O—H(g)  H—O—H(g) + ½O==O(g)

A. – 102

7. When the solids Ba(OH)₂ and NH₄SCN are mixed, a solution is produced and the temperature drops.

Ba(OH)₂(s) + 2NH₄SCN(s) → Ba(SCN)₂(aq) + 2NH₃(g) + 2H₂O(l)

Which statement about the energetics of this reaction is correct?

B. The reaction is endothermic and H is positive.

8. Using the equations below

Cu(s) + ½O₂(g) → CuO(s) ∆Hο= –156 kJ

2Cu(s) + ½O₂(g) → Cu₂O(s) ∆Hο= –170 kJ

what is the value of ∆Hο (in kJ) for the following reaction?

2CuO(s) → Cu₂O(s) + ½O₂(g)

A. 142

9. Which of the quantities in the enthalpy level diagram below is (are) affected by the use of a catalyst Time

C. I and II only

10. Consider the following equations.

Mg(s) + ½O₂(g) → MgO(s) ∆Hο = –602 kJ
H₂(g) + ½O₂(g) → H₂O(g) ∆Hο = –242 kJ

What is the ∆H° value (in kJ) for the following reaction?

MgO(s) + H₂(g) → Mg(s) + H₂O(g)

C. +360

11. For which of the following is the sign of the enthalpy change different from the other three?

D. 2Cl(g) → Cl₂(g)

12. Separate solutions of HCl(aq) and H₂SO₄(aq) of the same concentration and same volume were completely neutralized by NaOH(aq). X kJ and Y kJ of heat were evolved respectively. Which statement is correct?

B. Y = 2X

13. Which statements are correct for an endothermic reaction?

I. The system absorbs heat.

II. The enthalpy change is positive.

III. The bond enthalpy total for the reactants is greater than for the products.

A. I and II only

14. The mass m (in g) of a substance of specific heat capacity c (in J g^–1 K^–1 ) increases by t°C. What is the heat change in J?

A. mct

15. The average bond enthalpy for the C―H bond is 412 kJ mol^–1. Which process has an enthalpy change closest to this value?

D. CH₄(g) → CH₃(g) + H(g)

16. The following equation shows the formation of magnesium oxide from magnesium metal.

2Mg(s) + O₂(g)2MgO(s) H^Ө = –1204kJ

D. 1204 kJ of energy are released for every two mol of magnesium oxide formed.

17. The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.

C(s) +O₂(g)  CO₂(g) H^Ө = –x kJ mol^–1

CO(g) + ½O₂(g) CO₂(g) H^Ө = –y kJ mol^–l

What is the enthalpy change, in kJ mol^–1, for the oxidation of carbon to carbon monoxide?

C(s) + ½O₂(g) CO(g)

C. y – x

18. A simple calorimeter was used to determine the enthalpy of combustion of ethanol. The experimental value obtained was –920 kJ mol^–1. The Data Booklet value is –1371 kJ mol^–1. Which of the following best explains the difference between the two values?

B. Heat loss to the surroundings

19. For the reaction

2H₂(g) + O₂(g)  2H₂O(g)

the bond enthalpies (in kJ mol^–1) are

H–H	x
O=O	y
O–H	z

Which calculation will give the value, in kJ mol^–1, of H^Ө for the reaction?

C. 2x + y – 4z

20. Which statement about bond enthalpies is correct?

C. Bond breaking is endothermic and bond making is exothermic.

21. An equation for a reaction in which hydrogen is formed is

CH₄ + H₂O  3H₂ + CO H^Ө = +210 kJ

Which energy change occurs when 1 mol of hydrogen is formed in this reaction?

A. 70 kJ of energy are absorbed from the surroundings.

22. The equations and enthalpy changes for two reactions used in the manufacture of sulfuric acid are:

S(s) O₂(g)  SO₂(g) H^Ө = –300 kJ

2SO₂(g) + O₂(g)  2SO₃(g) H^Ө = –200 kJ

What is the enthalpy change, in kJ, for the reaction below?

2S(s) + 3O₂(g)  2SO₃(g)

D. –800

23. Approximate values of the average bond enthalpies, in kJ mol^–1, of three substances are:

H–H	430
F–F	155
H–F	565

What is the enthalpy change, in kJ, for this reaction?

2HF  H₂ + F₂

A. +545

24. The standard enthalpy change of formation values of two oxides of phosphorus are:

P₄(s) + 3O₂(g)  P₄O₆(s) H^Ө_f= –1600 kJ mol^–1

P₄(s) + 5O₂(g)  P₄O₁₀(s) H^Ө_f= –3000 kJ mol^–1

What is the enthalpy change, in kJ mol^–1, for the reaction below?

P₄O₆(s) + 2O₂(g)  P₄O₁₀(s)

C. –1400

25. Which statement is correct for an endothermic reaction?

C. The reactants are more stable than the products and H is positive.

26. Which statement is correct about the reaction shown?

2SO₂(g) + O₂(g)  2SO₃(g) H = –196 kJ

C. 98 kJ of energy are released for every mole of SO₂(g) reacted.

27. Which statements are correct for all exothermic reactions?

I. The enthalpy of the products is less than the enthalpy of the reactants.

II. The sign of H is negative.

III. The reaction is rapid at room temperature.

A. I and II only

28. Consider the specific heat capacity of the following metals.

Metal	Specific heat capacity / J kg^–1 K^–1
Cu	385
Ag	234
Au	130
Pt	134

Which metal will show the greatest temperature increase if 50 J of heat is supplied to a 0.001 kg sample of each metal at the same initial temperature?

C. Au

29. Consider the following reactions.

S(s) + O₂(g)  SO₃(g) H^Ө = 395 kJ mol^1

SO₂(s) + ½O₂(g)  SO₃(g) H^Ө = 98 kJ mol^–1

What is the H^Ө value (in kJ mol^–1) for the following reaction?

S(s) + O₂(g)  SO₂(g)

A. –297

30. Which statement is correct for an endothermic reaction?

B. Bonds in the reactants are stronger than the bonds in the products.

31. According to the enthalpy level diagram below, what is the sign for H and what term is used to refer to the reaction?

	H	Reaction
B	Negative	Exothermic

32. When 40 joules of heat are added to a sample of solid H₂O at –16.0°C the temperature increases to –8.0°C. What is the mass of the solid H₂O sample? [Specific heat capacity of H₂O(s) = 2.0 J g^–1K^–1]

A. 2.5 g

33. The H^Ө values for the formation of two oxides of nitrogen are given below.

N₂(g) + O₂(g)  2NO₂(g) H^Ө = –57 kJ mol^–1

N₂(g) + 2O₂(g)  N₂O₄(g) H^Ө = +9 kJ mol^–1

Use these values to calculate H^Ө for the following reaction (in kJ):

2NO₂(g)  N₂O₄(g)

D. +123

34. How much energy, in joules, is required to increase the temperature of 2.0 g of aluminium from 25 to 30°C? (Specific heat of Al = 0.90 J g^–1 K^–1).

C. 9.0

35. Which combination is correct for a chemical reaction that absorbs heat from the surroundings?

	Type of reaction	ΔH at constant pressure
c	Endothermic	Positive

36. Using the equations below:

C(s) + O₂(g) → CO₂(g) ∆Hο = –394 kJ mol^–1

Mn(s) + O₂(g) → MnO₂(s) ∆Hο = –520 kJ mol^–1

What is ∆H, in kJ, for the following reaction?

MnO₂(s) + C(s) → Mn(s) + CO₂(g)

B. 126

Stoichiometry and Thermochemistry MCQ Practice with Answers

Topic 1: Stoichiometry

Questions and Answers

1. What amount of oxygen, O2, (in moles) contains 1.8×1022 molecules?

2. Which compound has the empirical formula with the greatest mass?

3. __C2H2(g) + __O2(g) → __ CO2(g) + __ H2O(g)

4. 3.0 dm3 of sulfur dioxide is reacted with 2.0 dm3 of oxygen according to the equation below.

5. What will happen to the volume of a fixed mass of gas when its pressure and temperature (in Kelvin) are both doubled?

6. What amount (in moles) is present in 2.0 g of sodium hydroxide, NaOH?

7. A hydrocarbon contains 90% by mass of carbon. What is its empirical formula?

8. Copper can react with nitric acid as follows.

9. Lithium hydroxide reacts with carbon dioxide as follows.

10. Which change in conditions would increase the volume of a fixed mass of gas?

11. How many hydrogen atoms are contained in one mole of ethanol, C2H5OH?

12. The percentage by mass of the elements in a compound is C = 72%, H = 12%, O = 16%. What is the mole ratio of C:H in the empirical formula of this compound?

13. What is the coefficient for O2(g) when the equation below is balanced?

14. What amount of NaCl (in moles) is required to prepare 250 cm3 of a 0.200 mol dm–3 solution?

15. For which set of conditions does a fixed mass of an ideal gas have the greatest volume?

16. Which of the following contains the greatest number of molecules?

17. Which of the following compounds has/have the empirical formula CH2O?

18. Assuming complete reaction, what volume of 0.200 mol dm–3 HCl(aq) is required to neutralize 25.0 cm3 of 0.200 mol dm–3 Ba(OH)2(aq)?

19. Under what conditions would one mole of methane gas, CH4, occupy the smallest volume?

20. The temperature in Kelvin of 2.0 dm3 of an ideal gas is doubled and its pressure is increased by a factor of four. What is the final volume of the gas?

21. Which is a correct definition of the term empirical formula?

22. The reaction of ethanal and oxygen can be represented by the unbalanced equation below.

23. The equation for the complete combustion of butane is

24. Which solution contains the greatest amount (in mol) of solute?

25. A fixed mass of an ideal gas has a volume of 800 cm3 under certain conditions. The pressure (in kPa) and temperature (in K) are both doubled. What is the volume of the gas after these changes with other conditions remaining the same?

26. The complete oxidation of propane produces carbon dioxide and water as shown below.

27. The relative molecular mass (Mr) of a compound is 60. Which formulas are possible for this compound?

28. Which sample has the least number of atoms?

29. Avogadro’s constant has the same value as the number of

30. What is the total of all the coefficients in the balanced equation for the reduction of 1 mol of MnO4–?

31. Which contains the same number of ions as the value of Avogadro’s constant?

32. A reaction occurring in the extraction of lead from its ore can be represented by this unbalanced equation:

33. The equation for a reaction occurring in the synthesis of methanol is

34. Which solution contains 0.1 mol of sodium hydroxide?

35. A cylinder of gas is at a pressure of 40 kPa. The volume and temperature (in K) are both doubled. What is the pressure of the gas after these changes?

36. Which of the following quantities has units?

37. The empirical formula of a compound is C2H4O. Which molecular formulas are possible for this compound?

38. Calcium carbonate decomposes on heating as shown below.

39. Sodium reacts with water as shown below.

40. What is the total number of ions present in the formula, Al2(SO4)3?

41. A 4 g sample of sodium hydroxide, NaOH, is dissolved in water and made up to 500 cm3 of aqueous solution. What is the concentration of the resulting solution?

42. Methane, CH4, burns in oxygen gas to form carbon dioxide and water. How many moles of carbon dioxide will be formed from 8.0 g of methane?

43. What is the empirical formula of a compound containing 50% by mass of element X (Ar = 20) and 50% by mass of element Y (Ar = 25)?

44. Assuming complete reaction, what volume of 0.200 mol dm–3 potassium hydroxide solution (KOH(aq)), is required to neutralize 25.0 cm3 of 0.200 mol dm–3 aqueous sulfuric acid, (H2SO4(aq))?

45. Consider the following reaction.

46. The temperature in Kelvin of 1.0 dm3 of an ideal gas is doubled and its pressure is tripled. What is the final volume of the gas in dm3?

47. On complete combustion, a sample of a hydrocarbon compound produces 1.5 mol of carbon dioxide and 2.0 mol of water. What is the molecular formula of this hydrocarbon?

48. When excess BaCl2(aq) was added to a sample of Fe(NH4)2(SO4)2(aq) to determine the amount in moles of sulfate present, 5.02×10–3 mol of BaSO4 was obtained. How many moles of sulfate ions and iron ions were in the sample of Fe(NH4)2(SO4)2?

49. What volume of 0.500 mol dm–3 sulfuric acid solution is required to react completely with 10.0 g of calcium carbonate according to the equation below?

50. Which expression gives the amount (in mol) of a substance, if the mass is given in grams?

51. What is the total number of atoms in 0.20 mol of propanone, CH3COCH3?

52. When the equation below is balanced for 1 mol of C3H4, what is the coefficient for O2?

53. Ethyne, C2H2, reacts with oxygen according to the equation below. What volume of oxygen (in dm3) reacts with 0.40 dm3 of C2H2?

54. Ethyne, C2H2, reacts with oxygen according to the equation below. What volume of oxygen (in dm3) reacts with 0.40 dm3 of C2H2?

55. What is the coefficient for H+ when the redox equation below is balanced?

56. How many hydrogen atoms are in one mole of ethanol, C2H5OH?

57. What is the coefficient for H2SO4(aq) when the following equation is balanced, using the smallest possible integers?

58. Air bags in cars inflate when sodium azide decomposes to form sodium and nitrogen:

59. What volume, in cm3, of 0.200 mol dm–3 HCl(aq) is required to neutralize 25.0 cm3 of 0.200 mol dm–3 Ba(OH)2(aq)?

Topic 5: Thermochemistry

Questions

1.

2. The temperature of a 2.0 g sample of aluminium increases from 25°C to 30°C. How many joules of heat energy were added? (Specific heat of Al = 0.90 J g–1K–1)

3. Using the equations below:

4. Which statements about exothermic reactions are correct?

5. A sample of a metal is heated. Which of the following are needed to calculate the heat absorbed by the sample?

6. The average bond enthalpies for O—O and O==O are 146 and 496 kJ mol–1 respectively. What is the enthalpy change, in kJ, for the reaction below?

7. When the solids Ba(OH)2 and NH4SCN are mixed, a solution is produced and the temperature drops.

8. Using the equations below

9. Which of the quantities in the enthalpy level diagram below is (are) affected by the use of a catalyst Time

10. Consider the following equations.

11. For which of the following is the sign of the enthalpy change different from the other three?

12. Separate solutions of HCl(aq) and H2SO4(aq) of the same concentration and same volume were completely neutralized by NaOH(aq). X kJ and Y kJ of heat were evolved respectively. Which statement is correct?

13. Which statements are correct for an endothermic reaction?

14. The mass m (in g) of a substance of specific heat capacity c (in J g–1 K–1 ) increases by t°C. What is the heat change in J?

15. The average bond enthalpy for the C―H bond is 412 kJ mol–1. Which process has an enthalpy change closest to this value?

16. The following equation shows the formation of magnesium oxide from magnesium metal.

1. What amount of oxygen, O₂, (in moles) contains 1.8×10²² molecules?

3. C₂H₂(g) + O₂(g) → CO₂(g) + H₂O(g)

4. 3.0 dm³ of sulfur dioxide is reacted with 2.0 dm³ of oxygen according to the equation below.

11. How many hydrogen atoms are contained in one mole of ethanol, C₂H₅OH?

13. What is the coefficient for O₂(g) when the equation below is balanced?

14. What amount of NaCl (in moles) is required to prepare 250 cm³ of a 0.200 mol dm^–3 solution?

17. Which of the following compounds has/have the empirical formula CH₂O?

18. Assuming complete reaction, what volume of 0.200 mol dm^–3 HCl(aq) is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 Ba(OH)₂(aq)?

19. Under what conditions would one mole of methane gas, CH₄, occupy the smallest volume?

20. The temperature in Kelvin of 2.0 dm³ of an ideal gas is doubled and its pressure is increased by a factor of four. What is the final volume of the gas?

25. A fixed mass of an ideal gas has a volume of 800 cm³ under certain conditions. The pressure (in kPa) and temperature (in K) are both doubled. What is the volume of the gas after these changes with other conditions remaining the same?

27. The relative molecular mass (M_r) of a compound is 60. Which formulas are possible for this compound?

30. What is the total of all the coefficients in the balanced equation for the reduction of 1 mol of MnO₄^–?

37. The empirical formula of a compound is C₂H₄O. Which molecular formulas are possible for this compound?

40. What is the total number of ions present in the formula, Al₂(SO₄)₃?

41. A 4 g sample of sodium hydroxide, NaOH, is dissolved in water and made up to 500 cm³ of aqueous solution. What is the concentration of the resulting solution?

42. Methane, CH₄, burns in oxygen gas to form carbon dioxide and water. How many moles of carbon dioxide will be formed from 8.0 g of methane?

43. What is the empirical formula of a compound containing 50% by mass of element X (A_r = 20) and 50% by mass of element Y (A_r = 25)?

44. Assuming complete reaction, what volume of 0.200 mol dm^–3 potassium hydroxide solution (KOH(aq)), is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 aqueous sulfuric acid, (H₂SO₄(aq))?

46. The temperature in Kelvin of 1.0 dm³ of an ideal gas is doubled and its pressure is tripled. What is the final volume of the gas in dm³?

48. When excess BaCl₂(aq) was added to a sample of Fe(NH₄)₂(SO₄)₂(aq) to determine the amount in moles of sulfate present, 5.02×10^–3 mol of BaSO₄ was obtained. How many moles of sulfate ions and iron ions were in the sample of Fe(NH₄)₂(SO₄)₂?

49. What volume of 0.500 mol dm^–3 sulfuric acid solution is required to react completely with 10.0 g of calcium carbonate according to the equation below?

51. What is the total number of atoms in 0.20 mol of propanone, CH₃COCH₃?

52. When the equation below is balanced for 1 mol of C₃H₄, what is the coefficient for O₂?

53. Ethyne, C₂H₂, reacts with oxygen according to the equation below. What volume of oxygen (in dm³) reacts with 0.40 dm³ of C₂H₂?

54. Ethyne, C₂H₂, reacts with oxygen according to the equation below. What volume of oxygen (in dm³) reacts with 0.40 dm³ of C₂H₂?

55. What is the coefficient for H⁺ when the redox equation below is balanced?

56. How many hydrogen atoms are in one mole of ethanol, C₂H₅OH?

57. What is the coefficient for H₂SO₄(aq) when the following equation is balanced, using the smallest possible integers?

59. What volume, in cm³, of 0.200 mol dm^–3 HCl(aq) is required to neutralize 25.0 cm³ of 0.200 mol dm^–3 Ba(OH)₂(aq)?

2. The temperature of a 2.0 g sample of aluminium increases from 25°C to 30°C. How many joules of heat energy were added? (Specific heat of Al = 0.90 J g^–1K^–1)

6. The average bond enthalpies for O—O and O==O are 146 and 496 kJ mol^–1 respectively. What is the enthalpy change, in kJ, for the reaction below?

7. When the solids Ba(OH)₂ and NH₄SCN are mixed, a solution is produced and the temperature drops.

12. Separate solutions of HCl(aq) and H₂SO₄(aq) of the same concentration and same volume were completely neutralized by NaOH(aq). X kJ and Y kJ of heat were evolved respectively. Which statement is correct?

14. The mass m (in g) of a substance of specific heat capacity c (in J g^–1 K^–1 ) increases by t°C. What is the heat change in J?

15. The average bond enthalpy for the C―H bond is 412 kJ mol^–1. Which process has an enthalpy change closest to this value?

18. A simple calorimeter was used to determine the enthalpy of combustion of ethanol. The experimental value obtained was –920 kJ mol^–1. The Data Booklet value is –1371 kJ mol^–1. Which of the following best explains the difference between the two values?

23. Approximate values of the average bond enthalpies, in kJ mol^–1, of three substances are:

32. When 40 joules of heat are added to a sample of solid H₂O at –16.0°C the temperature increases to –8.0°C. What is the mass of the solid H₂O sample? [Specific heat capacity of H₂O(s) = 2.0 J g^–1K^–1]

33. The H^Ө values for the formation of two oxides of nitrogen are given below.

34. How much energy, in joules, is required to increase the temperature of 2.0 g of aluminium from 25 to 30°C? (Specific heat of Al = 0.90 J g^–1 K^–1).