Q: Which of the following is the correct molar ratio for converting between moles of $A$ and moles of $B$ in a chemical reaction?

$\frac{\text{mol } B}{\text{mol } A}$

Q: Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

$\text{moles} = \frac{\text{mass}}{\text{molar mass}}$

Question 1

Which of the following best describes a double displacement reaction?

Accepted Answer

A reaction where two compounds exchange ions to form two new compounds, following the general form $AB + CD \rightarrow AD + CB$

Question 2

When balancing chemical equations by inspection, which of the following is a correct rule to follow?

Accepted Answer

You can change the coefficients in a reaction to make it balance, but you cannot change the subscripts

Question 3

Given the unbalanced reaction: $\mathrm{CH_3CHO} (g) + O_2 (g) \rightarrow CO_2 (g) + H_2O (l)$, what are the correct coefficients to balance the equation?

Accepted Answer

$2\ \mathrm{CH_3CHO} + 5\ O_2 \rightarrow 4\ CO_2 + 4\ H_2O$

Question 4

A student is asked to balance the following equation: $\mathrm{FeO} + C \rightarrow Fe + CO$. What is the correct set of coefficients?

Accepted Answer

$1\ \mathrm{FeO} + 1\ C \rightarrow 1\ Fe + 1\ CO$

Question 5

Which statement about limiting reactants is correct?

Accepted Answer

The limiting reactant is the reactant that is completely consumed first, thus determining the maximum amount of product formed

Question 6

If you have 10 mol of $O_2$ and want to react it with $NH_3$ according to the equation $4\ NH_3 + 5\ O_2 \rightarrow 4\ NO + 6\ H_2O$, how many moles of $NH_3$ are needed?

Accepted Answer

$8\ 	ext{mol}$

Question 7

A 1.256 g sample of elemental sulfur reacts with fluorine to form $SF_x$. If 5.722 g of $SF_x$ is isolated, what is the value of $x$?

Accepted Answer

$6$

Question 8

Which of the following is the correct molecular formula for aspirin, given it is composed of 60.02% C, 35.55% O, and 4.43% H, with a molar mass between 150–200 g/mol?

Accepted Answer

$C_9H_8O_4$

Question 9

In a precipitation reaction, $KBr (aq) + AgNO_3 (aq) \rightarrow KNO_3 (aq) + AgBr (s)$, if you mix 0.050 mol $KBr$ and 0.050 mol $AgNO_3$, how many moles of $AgBr$ will precipitate?

Accepted Answer

$0.050\ 	ext{mol}$

Question 10

Which of the following is the correct net ionic equation for the reaction between $NaI (aq)$ and $Pb(NO_3)_2 (aq)$?

Accepted Answer

$2\ I^- (aq) + Pb^{2+} (aq) \rightarrow PbI_2 (s)$

Question 11

Which of the following is NOT a step in balancing chemical equations by inspection?

Accepted Answer

Changing the subscripts of compounds to balance the equation

Question 12

In the reaction $4\ NH_3 + 5\ O_2 ightarrow 4\ NO + 6\ H_2O$, if you start with 40.0 g $NH_3$ and excess $O_2$, how many grams of $NO$ will be produced? ($M_{NH_3} = 17.0\ 	ext{g/mol}$, $M_{NO} = 30.0\ 	ext{g/mol}$)

Accepted Answer

$28.2\ 	ext{g}$

Question 13

Which of the following is the correct molar ratio for converting between moles of $A$ and moles of $B$ in a chemical reaction?

Accepted Answer

$\frac{	ext{mol } B}{	ext{mol } A}$

Question 14

Which of the following is a correct statement about solution dilution?

Accepted Answer

The number of moles of solute remains constant before and after dilution

Question 15

If you need to prepare 250.0 mL of a 0.100 M $NaCl$ solution from a 0.500 M stock solution, what volume of stock solution should you use?

Accepted Answer

$50.0\ 	ext{mL}$

Question 16

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$	ext{moles} = \frac{	ext{mass}}{	ext{molar mass}}$

Question 17

In a redox reaction, which species is reduced?

Accepted Answer

The species whose oxidation number decreases

Question 18

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

$CH_4 + 2\ O_2 \rightarrow CO_2 + 2\ H_2O$

General Chemistry: Reaction Types, Balancing Equations, Stoichiometry, and Limiting Reactants

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