CH 3 PART 4

Question 2

What is a limiting reagent?

Answer 2

The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product formed.

Question 3

True or False: The excess reagent is the reactant that is completely used up in a reaction.

Answer 3

False

Question 4

In the reaction 2H2 + O2 → 2H2O, what is the limiting reagent if you have 3 moles of H2 and 1 mole of O2?

Answer 4

O2

Question 5

Fill in the blank: Theoretical yield is the maximum amount of product that can be formed from a given amount of _______.

Answer 5

reactants

Question 6

What is the formula to calculate percent yield?

Answer 6

Percent yield = (actual yield / theoretical yield) x 100%

Question 7

If you start with 5 grams of A and 10 grams of B, how do you determine the limiting reagent?

Answer 7

Calculate the moles of each reactant and compare the mole ratios required by the balanced equation.

Question 8

True or False: The actual yield is always equal to the theoretical yield.

Answer 8

False

Question 9

What is the purpose of stoichiometry in chemical reactions?

Answer 9

To calculate the relationships between reactants and products in a chemical reaction.

Question 10

If the theoretical yield of a reaction is 20 grams and the actual yield is 15 grams, what is the percent yield?

Answer 10

75%

Question 11

What is the first step in a limiting reagent calculation?

Answer 11

Write and balance the chemical equation.

Question 12

Multiple Choice: Which of the following is NOT a reason for a lower actual yield? A) Incomplete reaction B) Loss of product during transfer C) Excess reagent D) Measurement error

Answer 12

C) Excess reagent

Question 13

Define ‘excess reagent’.

Answer 13

The reactant that remains after the limiting reagent is completely consumed.

Question 14

What is the effect of a limiting reagent on the amount of product formed?

Answer 14

It determines the maximum amount of product that can be produced.

Question 15

True or False: A reaction can have multiple limiting reagents.

Answer 15

False

Question 16

In a reaction, if you have 4 moles of A and 6 moles of B, and the balanced equation is A + 2B → C, what is the limiting reagent?

Answer 16

A

Question 17

What does it mean if a reaction has a high percent yield?

Answer 17

It indicates that the reaction was efficient and most of the reactants were converted to products.

Question 18

Fill in the blank: To find the limiting reagent, you must compare the _______ of each reactant to the coefficients in the balanced equation.

Answer 18

moles

Question 19

What is the role of the balanced chemical equation in stoichiometry?

Answer 19

It provides the mole ratios needed to relate reactants and products.

Question 20

Multiple Choice: Which calculation helps determine how much product can be formed? A) Density calculation B) Limiting reagent calculation C) Temperature calculation D) Pressure calculation

Answer 20

B) Limiting reagent calculation

Question 21

True or False: All reactions have a limiting reagent.

Answer 21

True

Question 22

What is the balanced equation for the combustion of propane (C3H8)?

Answer 22

C3H8 + 5O2 → 3CO2 + 4H2O

Question 23

If you have 2 moles of C3H8 and 10 moles of O2, which is the limiting reagent?

Answer 23

C3H8

Question 24

What does the term ‘actual yield’ refer to?

Answer 24

The amount of product actually obtained from a reaction.

Question 25

Fill in the blank: Theoretical yield assumes that the reaction goes to _______.

Answer 25

completion

Question 26

What can affect the actual yield of a reaction aside from the limiting reagent?

Answer 26

Side reactions, incomplete reactions, and loss of product.

Question 27

Multiple Choice: Which of the following represents an incomplete reaction? A) All reactants converted B) Some reactants remain C) Excess product produced D) None of the above

Answer 27

B) Some reactants remain

Question 28

What is the significance of knowing the limiting reagent in industrial processes?

Answer 28

It helps optimize the use of materials and reduce waste.

Question 29

True or False: In a balanced equation, the coefficients represent the number of moles of each substance.

Answer 29

True

Question 30

How do you convert grams of a reactant to moles?

Answer 30

Use the formula: moles = grams / molar mass.

Question 31

What is the molar mass of water (H2O)?

Answer 31

18.02 g/mol

Question 32

If the theoretical yield is 50 grams and the actual yield is 40 grams, how would you express this as a fraction?

Answer 32

40/50 or 0.8

Question 33

What is the relationship between limiting reagent and reaction yield?

Answer 33

The limiting reagent determines the maximum theoretical yield of the reaction.

Question 34

Multiple Choice: Which factor does NOT affect reaction yield? A) Temperature B) Pressure C) Concentration D) Color of reactants

Answer 34

D) Color of reactants