Question 1

Which of the following best describes the purpose of balancing a chemical equation?

Accepted Answer

To make sure the type and number of atoms on both sides of the equation are equal.

Question 2

Given the unbalanced equation: $\mathrm{C_4H_{10} (g) + O_2 (g) \rightarrow H_2O (l) + CO_2 (g)}$, what is the correct set of coefficients to balance the equation?

Accepted Answer

$1, 6.5, 5, 4$

Question 3

In the balanced equation $2\mathrm{H_2 (g) + 1\ O_2 (g) \rightarrow 2\ H_2O (g)}$, what does the coefficient '2' in front of $\mathrm{H_2}$ represent?

Accepted Answer

The number of $\mathrm{H_2}$ molecules involved in the reaction.

Question 4

When balancing the equation $\mathrm{Na_3PO_4 (aq) + Ca(NO_3)_2 (aq) \rightarrow NaNO_3 (aq) + Ca_3(PO_4)_2 (aq)}$, what is the sum of the coefficients after balancing?

Accepted Answer

$1 + 4.5 + 4.5 + 1 = 11$

Question 5

If a polyatomic ion is present on both sides of a chemical equation, what is the recommended strategy for balancing?

Accepted Answer

Treat the polyatomic ion as a single unit.

Question 6

What is the total sum of the coefficients after balancing the equation $\mathrm{C_2H_5SH (g) + O_2 (g) \rightarrow CO_2 (g) + H_2O (l) + SO_2 (g)}$?

Accepted Answer

$1 + 4.5 + 2 + 3 + 1 = 11.5$

Question 7

Why might a decimal or fraction appear as a coefficient when balancing a chemical equation?

Accepted Answer

To temporarily balance the equation before multiplying all coefficients by a common factor.

Question 8

In the reaction $\mathrm{2H_2 (g) + O_2 (g) \rightarrow 2H_2O (g)}$, how many total molecules of gas are present before the reaction occurs?

Accepted Answer

$3$

Question 9

Which step is NOT part of the recommended process for balancing chemical equations?

Accepted Answer

Change the subscripts of compounds to balance atoms.

Question 10

A student balances the equation $\mathrm{C_4H_{10} (g) + O_2 (g) \rightarrow H_2O (l) + CO_2 (g)}$ and gets the coefficients $2, 13, 10, 8$. What mistake did the student most likely make?

Accepted Answer

They multiplied all coefficients by 2 instead of leaving them in the lowest whole number ratio.

Question 11

In the equation $\mathrm{Na_3PO_4 (aq) + Ca(NO_3)_2 (aq) \rightarrow NaNO_3 (aq) + Ca_3(PO_4)_2 (aq)}$, which compound contains a polyatomic ion?

Accepted Answer

$\mathrm{Ca(NO_3)_2}$

Question 12

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

Accepted Answer

Coefficients indicate the number of molecules or moles involved in the reaction.

Question 13

If you have the balanced equation $\mathrm{2H_2 (g) + O_2 (g) \rightarrow 2H_2O (g)}$, how many moles of $\mathrm{H_2O}$ are produced from 4 moles of $\mathrm{H_2}$?

Accepted Answer

$4$

Question 14

Which of the following is a real-world application of balancing chemical equations?

Accepted Answer

Determining the amount of reactants needed for a pharmaceutical synthesis.

Question 15

A chemical reaction produces $\mathrm{5H_2O (l)}$ and $\mathrm{4CO_2 (g)}$ from $\mathrm{C_4H_{10} (g)}$ and $\mathrm{O_2 (g)}$. What is the minimum number of $\mathrm{O_2}$ molecules required for the reaction?

Accepted Answer

$6.5$

Balancing Chemical Equations in GOB Chemistry

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