Question 1

Which of the following statements best describes a balanced chemical equation?

Accepted Answer

It has the same number of atoms of each element on both sides of the equation.

Question 2

What is the balanced equation for the reaction of zinc metal with hydrochloric acid?

Accepted Answer

$$ \mathrm{Zn} + 2\mathrm{HCl} \rightarrow \mathrm{ZnCl}_2 + \mathrm{H}_2 $$

Question 3

When balancing equations, which element is typically left until last, especially in combustion reactions?

Accepted Answer

Oxygen and hydrogen

Question 4

Balance the following equation: $$ \mathrm{C}_2\mathrm{H}_6 + \mathrm{O}_2 \rightarrow \mathrm{CO}_2 + \mathrm{H}_2\mathrm{O} . $$What are the correct coefficients?

Accepted Answer

$$ 2\mathrm{C}_2\mathrm{H}_6 + 7\mathrm{O}_2 \rightarrow 4\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} $$

Question 5

Which practical tip is recommended when balancing equations containing polyatomic ions?

Accepted Answer

Balance the polyatomic ion as a group, not as separate atoms.

Question 6

What is the balanced equation for the decomposition of hydrogen peroxide?

Accepted Answer

$$ 2\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2 $$

Question 7

In the reaction $$ \mathrm{Al}_2\mathrm{O}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Al}_2\mathrm{(SO}_4)_3 + \mathrm{H}_2\mathrm{O} $$, what is the coefficient for $$ \mathrm{H}_2\mathrm{SO}_4  in $$the balanced equation?

Accepted Answer

3

Question 8

Which of the following is a correct step when balancing a chemical equation?

Accepted Answer

Adjust the leading coefficients to get the number of each kind of atom on both sides of the equation equal.

Question 9

Balance the following equation: $$ \mathrm{KClO}_3 \rightarrow \mathrm{KCl} + \mathrm{O}_2 . $$What are the correct coefficients?

Accepted Answer

$$ 2\mathrm{KClO}_3 \rightarrow 2\mathrm{KCl} + 3\mathrm{O}_2 $$

Question 10

A student balances the equation $$ \mathrm{Mg(OH)}_2 + \mathrm{HBr} \rightarrow \mathrm{MgBr}_2 + \mathrm{H}_2\mathrm{O}  as$$ $$ \mathrm{Mg(OH)}_2 + 2\mathrm{HBr} \rightarrow \mathrm{MgBr}_2 + 2\mathrm{H}_2\mathrm{O} . $$What mistake did the student avoid?

Accepted Answer

Forgetting to balance both hydrogen and bromine atoms.

Question 11

Which of the following is the balanced equation for the reaction: $$ \mathrm{Na}_2\mathrm{SO}_3 + \mathrm{Cl}_2 + \mathrm{HCl} \rightarrow \mathrm{NaHSO}_4 + \mathrm{HCl} $$?

Accepted Answer

Question 12

In the reaction $$ \mathrm{Al} + \mathrm{Fe}_2\mathrm{O}_3 \rightarrow \mathrm{Al}_2\mathrm{O}_3 + \mathrm{Fe} $$, what type of reaction is this?

Accepted Answer

Redox (thermite reaction)

Question 13

Which of the following is the correct balanced equation for the reaction: $$ \mathrm{Ca(OH)}_2 + \mathrm{HCl} \rightarrow \mathrm{CaCl}_2 + \mathrm{H}_2\mathrm{O} $$?

Accepted Answer

$$ \mathrm{Ca(OH)}_2 + 2\mathrm{HCl} \rightarrow \mathrm{CaCl}_2 + 2\mathrm{H}_2\mathrm{O} $$

Question 14

A student is asked to balance the equation $$ \mathrm{Li}_2\mathrm{CO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Li}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2 . $$What is the coefficient for $$ \mathrm{H}_2\mathrm{SO}_4 $$?

Accepted Answer

1

Question 15

Which of the following is a correct statement about coefficients in a balanced equation?

Accepted Answer

Coefficients are placed in front of atoms or compounds to show multipliers.

Question 16

Balance the following equation: $$ \mathrm{PCl}_3 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_3\mathrm{PO}_3 + \mathrm{HCl} . $$What are the correct coefficients?

Accepted Answer

$$ \mathrm{PCl}_3 + 3\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_3\mathrm{PO}_3 + 3\mathrm{HCl} $$

Question 17

In the reaction $$ \mathrm{Cu} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{CuSO}_4 + \mathrm{SO}_2 + \mathrm{H}_2\mathrm{O} $$, what is the coefficient for $$ \mathrm{H}_2\mathrm{SO}_4  in $$the balanced equation?

Accepted Answer

2

Question 18

Which of the following is the correct balanced equation for the reaction: $$ \mathrm{NH}_4^+ + \mathrm{NO}_2^- \rightarrow \mathrm{N}_2 + \mathrm{H}_2\mathrm{O} $$?

Accepted Answer

$$ \mathrm{NH}_4^+ + \mathrm{NO}_2^- \rightarrow \mathrm{N}_2 + 2\mathrm{H}_2\mathrm{O} $$

Question 19

A student is balancing the equation $$ \mathrm{ClO}_2 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{HClO}_3 + \mathrm{HCl} . $$What is the coefficient for $$ \mathrm{ClO}_2  in $$the balanced equation?

Accepted Answer

3

Balancing Chemical Equations: Principles, Steps, and Practice Problems

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