Q: How many molecules are present in $0.250$ mole of $CO_2$?

$1.51 \times 10^{23}$ molecules

Q: Which of the following is the correct formula for calculating percent yield?

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

Q: Methane ($CH_4$) has a molar mass of $16.04\ g/mol$. How many molecules are present in $32.08$ grams of methane?

$1.20 \times 10^{24}$ molecules

Question 1

Which of the following best describes a combination (synthesis) reaction?

Accepted Answer

Two or more elements or compounds combine to form a single product.

Question 2

Given the balanced equation $2Al(s) + 3S(s) \rightarrow Al_2S_3(s)$, how many moles of sulfur are required to react completely with 4 moles of aluminum?

Accepted Answer

$6$ moles

Question 3

Which observation is NOT typically evidence of a chemical reaction?

Accepted Answer

Change in state from solid to liquid without any other change

Question 4

In the reaction $Zn(s) + 2HCl(aq) \rightarrow ZnCl_2(aq) + H_2(g)$, which species is oxidized?

Accepted Answer

Zn

Question 5

How many molecules are present in $0.250$ mole of $CO_2$?

Accepted Answer

$1.51 	imes 10^{23}$ molecules

Question 6

Aspirin has the formula $C_9H_8O_4$. How many moles of oxygen atoms are present in $0.200$ mole of aspirin?

Accepted Answer

$0.800$ moles

Question 7

What is the molar mass of $Li_2CO_3$ (lithium carbonate)?

Accepted Answer

$73.89\ g/mol$

Question 8

How many moles of $NaCl$ are present in $117$ grams of $NaCl$? (Molar mass of $NaCl = 58.44\ g/mol$)

Accepted Answer

$2.00$ moles

Question 9

Which law states that mass is conserved in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 10

In the reaction $2Ag(s) + S(s) \rightarrow Ag_2S(s)$, if you start with $215.8$ grams of silver and $32.07$ grams of sulfur, what is the mass of $Ag_2S$ produced?

Accepted Answer

$247.87$ grams

Question 11

If $6.0$ moles of $O_2$ react with excess $Fe$ according to $4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$, how many moles of $Fe_2O_3$ are produced?

Accepted Answer

$4.0$ moles

Question 12

Which of the following is the correct mole ratio between $Fe$ and $O_2$ in the reaction $4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$?

Accepted Answer

$4$ moles $Fe$ : $3$ moles $O_2$

Question 13

A student mixes $32.0$ grams of $N_2$ with excess $H_2$ in the reaction $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$. What mass of $NH_3$ can be produced? ($M_{N_2} = 28.02\ g/mol$, $M_{NH_3} = 17.04\ g/mol$)

Accepted Answer

$38.9$ grams

Question 14

In a reaction, $3.00$ moles of $CO$ and $5.00$ moles of $H_2$ are mixed to produce $CH_3OH$ via $CO(g) + 2H_2(g) \rightarrow CH_3OH(g)$. What is the limiting reactant?

Accepted Answer

$H_2$

Question 15

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

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

Question 16

Which statement about oxidation-reduction (redox) reactions is correct?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 17

Methane ($CH_4$) has a molar mass of $16.04\ g/mol$. How many molecules are present in $32.08$ grams of methane?

Accepted Answer

$1.20 	imes 10^{24}$ molecules

Question 18

Which type of reaction is represented by $2HgO(s) \rightarrow 2Hg(l) + O_2(g)$?

Accepted Answer

Decomposition

Question 19

A reaction produces $5.00$ grams of product, but the theoretical yield is $6.50$ grams. What is the percent yield?

Accepted Answer

$76.9\%$

Chemical Reactions and Quantities: Study Notes for Introductory Chemistry

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