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IB DP Chemistry Questions

1.3 Reacting Masses and Volumes

Question 1

When 10 grams of reactant A reacts with 20 grams of reactant B, only 15 grams of product C is produced. What is the percentage yield of this reaction?

A. 50%

B. 75%

C. 100%

D. 150%

Question 2

Which of the following statements best describes a limiting reactant?

A. The reactant that is completely consumed in a reaction.

B. The reactant that is present in excess.

C. The reactant that determines the amount of product formed.

D. Both A and C.

Question 3

In a balanced chemical equation, the number of atoms of each element on the reactant side is:

A. Greater than on the product side.

B. Lesser than on the product side.

C. Equal to the number on the product side.

D. Not related to the product side.

Question 4

If the actual yield of a reaction is 80 grams and the theoretical yield is 100 grams, what is the percentage yield?

A. 60%

B. 70%

C. 80%

D. 90%

Question 5

Which factor does NOT affect the percentage yield in real-world reactions?

A. Purity of reactants.

B. Temperature.

C. Catalysts.

D. Color of the reactants.

Question 6

a) Define the concept of a limiting reactant and explain its significance in predicting product yields. [3]

b) Given the reaction: 2H₂ + O₂ → 2H₂O, if 4 moles of hydrogen gas react with 2 moles of oxygen gas, identify the limiting reactant and the number of moles of water produced. [3]

Question 7

a) Describe the importance of balancing chemical equations in stoichiometric calculations. [3]

b) For the reaction: N₂ + 3H₂ → 2NH₃, if 28 grams of nitrogen gas reacts with an excess of hydrogen gas, calculate the mass of ammonia produced. (Given: Molar mass of N₂ = 28 g/mol, NH₃ = 17 g/mol) [3]

Question 8

a) Define the term 'percentage yield' and explain factors that might affect it in real-world reactions. [4]

b) If a reaction has a theoretical yield of 50 grams, but only 40 grams of product is obtained, calculate the percentage yield. [2]

Question 9

a) Define Avogadro's number and explain its significance in relating the macroscopic world to the atomic/molecular level. [3]

b) How many atoms are present in 2 moles of carbon? [2]

c) If you have 12 grams of carbon, how many moles of carbon atoms do you have? (Given: Molar mass of Carbon = 12 g/mol) [2]

Question 10

a) Describe the difference between an element, a compound, and a mixture. [3]

b) Given a sample containing iron and sulphur, how would you determine if it's a mixture or a compound? [3]

c) Why is the mole concept crucial for stoichiometric calculations? [2]

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