Q: Percent yield is calculated using which formula?

$$\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$$

Question 1

Which of the following best describes a chemical reaction?

Accepted Answer

A process in which one or more substances are changed into one or more different substances, involving the breaking and forming of chemical bonds.

Question 2

Which of the following is the correct balanced equation for the decomposition of potassium chlorate ($$KClO_3) to $$form potassium chloride and oxygen gas?

Accepted Answer

$$2KClO_3(s) \rightarrow 2KCl(s) + 3O_2(g)$$

Question 3

In the reaction $$2Fe(s) + 3CuSO_4(aq) \rightarrow Fe_2$(SO_4$)_3(aq) + 3Cu(s)$$, how many moles of copper are produced when 4 moles of iron react completely?

Accepted Answer

6 moles

Question 4

Which statement about coefficients in a balanced chemical equation is correct?

Accepted Answer

They specify the relative numbers of particles or moles of each substance involved in the reaction.

Question 5

Given the reaction $$C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)$$, how many grams of $$O_2$$ are required to completely react with 50.0 g of propane ($$C_3H_8$$)? (Molar masses: $$C_3H_8 = 44.1 g/$$mol, $$O_2 = 32.0$ g/mol)

Accepted Answer

182 g

Question 6

In the reaction $$2Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)$$, if you have 9.20 g of sodium metal, how many grams of sodium chloride can be produced? (Molar masses: $$Na = 23.0 g/$$mol, $$NaCl = 58.5 g/$$mol)

Accepted Answer

Question 7

Which of the following best defines the limiting reactant in a chemical reaction?

Accepted Answer

The reactant that is completely consumed and limits the amount of product formed.

Question 8

In the reaction $$2Mg(s) + O_2$(g) \rightarrow 2MgO(s)$$, 42.5 g of $$Mg is $$reacted with 33.8 g of $$O_2. $$Which reactant is limiting? (Molar masses: $$Mg = 24.3 g/$$mol, $$O_2 = 32.0$ g/mol)

Accepted Answer

$$Mg$$

Question 9

Percent yield is calculated using which formula?

Accepted Answer

$$	ext{Percent Yield} = \frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100$$

Question 10

A reaction of 16.7 g of $$Fe_2O_3$$ with 8.85 g of $$CO$$ produces 7.23 g of $$Fe. $$What is the percent yield of iron? (Molar masses: $$Fe_2O_3 = 159.7 g/$$mol, $$CO = 28.0 g/$$mol, $$Fe = 55.8 g/$$mol; reaction: $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2)$$

Accepted Answer

64.8%

Question 11

Which of the following is a combustion reaction?

Accepted Answer

$$CH_4(g) + 2O_2(g$$) \rightarrow $$CO_2(g) + 2H_2O(g$$)$$

Question 12

Which of the following statements about reactions of alkali metals is correct?

Accepted Answer

Alkali metals react more vigorously with water as you go down the group.

Question 13

If 5.00 g of $$NO_2$$ reacts in the atmosphere, what mass of $$HNO_3 is $$produced according to the reaction $$4NO_2(g) + O_2$(g) + 2H_2O(l) \rightarrow 4HNO_3(aq)$$? (Molar masses: $$NO_2 = 46.0$ g/mol, $$HNO_3$$ = 63.0 g/$$mol)

Accepted Answer

6.85 g

Question 14

Which of the following is NOT a sign of a chemical reaction?

Accepted Answer

Change in physical state without new substance formation

Question 15

In the reaction $$2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2$(g)$$, what volume of $$H_2$$ gas at STP (0°C, 1 atm) is produced from 4.60 g of $$Na$$? (Molar mass $$Na = 23.0 g/$$mol; 1 mol gas at STP = 22.4 L)

Accepted Answer

2.24 L

Question 16

Which of the following is the correct mole-to-mole ratio for $$C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)$$?

Accepted Answer

1 mol $$C_3H_8$$ : 5 mol $$O_2$$ : 3 mol $$CO_2$$ : 4 mol $$H_2O$$

Question 17

Which of the following is true about theoretical yield?

Accepted Answer

It is the maximum amount of product that can be made based on the amount of limiting reactant.

Question 18

Which of the following reactions represents the combustion of ethanol ($$C_2H_5OH$$)?

Accepted Answer

$$C_2H_5OH(l) + 3O_2(g) \rightarrow 2CO_2(g) + 3H_2O(g)$$

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