Q: Which of the following is the correct formula to convert mass of reactant A to mass of product B in a chemical reaction?

$$\text{mass A} \times \left( \frac{1\ \text{mol A}}{\text{molar mass A}} \right) \times \left( \frac{\text{mol B}}{\text{mol A}} \right) \times \left( \frac{\text{molar mass B}}{1\ \text{mol B}} \right)$$

Q: Which equation correctly expresses percent yield?

$$\frac{\text{actual yield}}{\text{theoretical yield}} \times 100$$

Question 1

Which of the following best describes a physical change?

Accepted Answer

A change that alters only the state or appearance, but not the composition, of a substance.

Question 2

Which of the following is a chemical change?

Accepted Answer

Rusting of iron.

Question 3

What is the balanced chemical equation for the combustion of methane?

Accepted Answer

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

Question 4

Which statement about chemical equations is FALSE?

Accepted Answer

They do not need to be balanced to obey the law of conservation of mass.

Question 5

In the reaction $$2C_8H_{18}(l) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g)$$, what is the mole ratio of $$O_2 to$$ $$CO_2$$?

Accepted Answer

$$25:16$$

Question 6

If 22.0 moles of $$C_8H_{18}$$ are combusted, how many moles of $$CO_2$$ are produced?

Accepted Answer

$$176$$ moles

Question 7

Which of the following is the correct formula to convert mass of reactant A to mass of product B in a chemical reaction?

Accepted Answer

$$	ext{mass A} 	imes \left( \frac{1\ 	ext{mol A}}{	ext{molar mass A}} ight) 	imes \left( \frac{	ext{mol B}}{	ext{mol A}} ight) 	imes \left( \frac{	ext{molar mass B}}{1\ 	ext{mol B}} ight)$$

Question 8

A pizza recipe requires 1 crust, 5 oz. tomato sauce, and 2 cups cheese for 1 pizza. If you have 4 crusts, 10 cups cheese, and 15 oz. tomato sauce, what is the limiting reactant?

Accepted Answer

Tomato sauce

Question 9

In a chemical reaction, the limiting reactant is:

Accepted Answer

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

Question 10

Which equation correctly expresses percent yield?

Accepted Answer

$$\frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$$

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 greenhouse gases is TRUE?

Accepted Answer

They allow sunlight to enter and prevent some heat from escaping.

Question 13

During the combustion of $$C_8H_{18}$$, how many moles of $$H_2O$$ are produced per mole of $$C_8H_{18}$$?

Accepted Answer

$$9$$

Question 14

Which of the following is NOT a step in balancing a chemical equation?

Accepted Answer

Change the subscripts in chemical formulas to balance atoms.

Question 15

A reaction produces 25.8 g of glucose ($$C_6H_{12}O_6$) from 37.8 g of CO_2$. What is the percent yield if the theoretical yield is 25.8 g?

Accepted Answer

$$100\%$$

Question 16

Which of the following reactions is an example of an alkali metal reacting with water?

Accepted Answer

$$2K(s) + 2H_2O(l) \rightarrow 2KOH(aq) + H_2$(g)$$

Question 17

Which of the following is the correct balanced equation for the reaction between strontium chloride and lithium phosphate to form strontium phosphate and lithium chloride?

Accepted Answer

$$3SrCl_2(aq) + 2Li_3PO_4(aq) \rightarrow Sr_3$(PO_4$)_2(s) + 6LiCl(aq)$$

Question 18

Which of the following is a correct statement about the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Chapter 7: Chemical Reactions and Chemical Quantities – Structured Study Notes

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