Question 1

Which of the following best describes the Law of Conservation of Mass as it applies to chemical equations?

Accepted Answer

The total mass of the reactants must equal the total mass of the products.

Question 2

Given the unbalanced equation $$\mathrm{CH_4$ + O_2$ \rightarrow CO_2$ + H_2O}$$, what are the correct coefficients to balance the equation?

Accepted Answer

$$1, 2, 1, 2$$

Question 3

In the reaction $$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}$$, how many molecules of water are produced from 4 molecules of hydrogen gas?

Accepted Answer

4

Question 4

Which of the following is NOT a correct guideline for balancing chemical equations?

Accepted Answer

Change the subscripts of compounds to balance atoms.

Question 5

If you have the reaction $$\mathrm{C_2H_6} + \mathrm{O_2$} \rightarrow \mathrm{CO_2$} + \mathrm{H_2O}$$, what is the first element you should try to balance according to the guidelines?

Accepted Answer

Carbon

Question 6

Which symbol in a chemical equation separates multiple reactants or products?

Accepted Answer

$$+$$

Question 7

A student tries to balance the equation $$\mathrm{H_2$} + \mathrm{O_2$} \rightarrow \mathrm{H_2O} by $$writing $$\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}. $$What is the error in this attempt?

Accepted Answer

There are not enough oxygen atoms on the reactant side.

Question 8

Which of the following best describes a reactant in a chemical equation?

Accepted Answer

A substance consumed during the reaction, present on the left side.

Question 9

In the combustion of methane, $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, how many total oxygen atoms are present among the products?

Accepted Answer

4

Question 10

Why is it incorrect to balance a chemical equation by changing the subscripts in chemical formulas?

Accepted Answer

It changes the identity of the substances involved.

Question 11

Which of the following is the correct balanced equation for the reaction of hydrogen and oxygen to form water?

Accepted Answer

$$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}$$

Question 12

In a chemical equation, what does the arrow ($$\rightarrow) $$represent?

Accepted Answer

It separates reactants from products, indicating the direction of the reaction.

Question 13

Which of the following is a product in the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 14

If a chemical equation is not balanced, which law is being violated?

Accepted Answer

Law of Conservation of Mass

Question 15

Which step should be performed LAST when balancing a chemical equation?

Accepted Answer

Balance oxygen atoms.

Chemical Reactions and Reaction Stoichiometry: Study Notes

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