Q: A sample of sodium chloride (NaCl) has a density of 4.28 g/cm$^3$. How many sodium atoms are present in 12.0 cm$^3$ of NaCl?

$12.0 \text{ cm}^3 \times \frac{4.28 \text{ g}}{1 \text{ cm}^3} \times \frac{1 \text{ mol NaCl}}{58.44 \text{ g}} \times \frac{1 \text{ mol Na}}{1 \text{ mol NaCl}} \times \frac{6.022 \times 10^{23} \text{ atoms Na}}{1 \text{ mol Na}}$

Q: A 2.00 M stock solution of HCl is used to prepare 100.0 mL of a 0.150 M solution. How many mL of stock solution are required?

$V_1 = \frac{M_2V_2}{M_1} = \frac{0.150 \times 100.0}{2.00} = 7.50 \text{ mL}$

Q: Chlorine reacts with potassium iodide according to the equation $Cl_2 + 2KI \rightarrow 2KCl + I_2$. How many grams of KI are required to completely react with 1.20 g of $Cl_2$?

$1.20 \text{ g } Cl_2 \times \frac{1 \text{ mol } Cl_2}{70.9 \text{ g } Cl_2} \times \frac{2 \text{ mol KI}}{1 \text{ mol } Cl_2} \times \frac{166.0 \text{ g KI}}{1 \text{ mol KI}} = 5.62 \text{ g KI}$

Q: Nitrogen reacts with hydrogen to form ammonia: $N_2 + 3H_2 \rightarrow 2NH_3$. What is the theoretical yield of ammonia if 3.40 g of nitrogen reacts with 1.50 g of hydrogen?

$3.40 \text{ g } N_2 \times \frac{1 \text{ mol } N_2}{28.02 \text{ g } N_2} \times \frac{2 \text{ mol NH}_3}{1 \text{ mol } N_2} \times \frac{17.03 \text{ g NH}_3}{1 \text{ mol NH}_3} = 4.14 \text{ g NH}_3$

Q: If 2.00 g of ammonia is produced in the reaction above, what is the percent yield?

$\frac{2.00}{4.14} \times 100\% = 48.3\%$

Q: You need to prepare 0.500 M solution of potassium chloride. How many grams of potassium chloride are required to make 1.00 L of solution?

$0.500 \text{ mol/L} \times 1.00 \text{ L} \times 74.55 \text{ g/mol} = 37.8 \text{ g KCl}$

Q: A solution is prepared by adding 2.00 mL of a 1.00 M stock solution to a 25.0 mL volumetric flask and diluting to the line with water. What is the final concentration of the solution?

$M_2 = \frac{M_1V_1}{V_2} = \frac{1.00 \times 2.00}{25.0} = 0.0800 \text{ M}$

Question 1

A sample of sodium chloride (NaCl) has a density of 4.28 g/cm$^3$. How many sodium atoms are present in 12.0 cm$^3$ of NaCl?

Accepted Answer

$12.0 	ext{ cm}^3 	imes \frac{4.28 	ext{ g}}{1 	ext{ cm}^3} 	imes \frac{1 	ext{ mol NaCl}}{58.44 	ext{ g}} 	imes \frac{1 	ext{ mol Na}}{1 	ext{ mol NaCl}} 	imes \frac{6.022 	imes 10^{23} 	ext{ atoms Na}}{1 	ext{ mol Na}}$

Question 2

Which of the following statements best describes the difference between precision and accuracy?

Accepted Answer

Precision refers to how close measurements are to each other, while accuracy refers to how close measurements are to the true value.

Question 3

A compound is determined to be 78.9% C, 7.06% H, and 14.0% O by mass. What is the empirical formula of the compound?

Accepted Answer

$C_6H_8O$

Question 4

If the molar mass of the compound in the previous question is 228.29 g/mol, what is its molecular formula?

Accepted Answer

$C_{12}H_{16}O_2$

Question 5

A 2.00 M stock solution of HCl is used to prepare 100.0 mL of a 0.150 M solution. How many mL of stock solution are required?

Accepted Answer

$V_1 = \frac{M_2V_2}{M_1} = \frac{0.150 	imes 100.0}{2.00} = 7.50 	ext{ mL}$

Question 6

Chlorine reacts with potassium iodide according to the equation $Cl_2 + 2KI \rightarrow 2KCl + I_2$. How many grams of KI are required to completely react with 1.20 g of $Cl_2$?

Accepted Answer

$1.20 	ext{ g } Cl_2 	imes \frac{1 	ext{ mol } Cl_2}{70.9 	ext{ g } Cl_2} 	imes \frac{2 	ext{ mol KI}}{1 	ext{ mol } Cl_2} 	imes \frac{166.0 	ext{ g KI}}{1 	ext{ mol KI}} = 5.62 	ext{ g KI}$

Question 7

Nitrogen reacts with hydrogen to form ammonia: $N_2 + 3H_2 \rightarrow 2NH_3$. What is the theoretical yield of ammonia if 3.40 g of nitrogen reacts with 1.50 g of hydrogen?

Accepted Answer

$3.40 	ext{ g } N_2 	imes \frac{1 	ext{ mol } N_2}{28.02 	ext{ g } N_2} 	imes \frac{2 	ext{ mol NH}_3}{1 	ext{ mol } N_2} 	imes \frac{17.03 	ext{ g NH}_3}{1 	ext{ mol NH}_3} = 4.14 	ext{ g NH}_3$

Question 8

If 2.00 g of ammonia is produced in the reaction above, what is the percent yield?

Accepted Answer

$\frac{2.00}{4.14} 	imes 100\% = 48.3\%$

Question 9

You need to prepare 0.500 M solution of potassium chloride. How many grams of potassium chloride are required to make 1.00 L of solution?

Accepted Answer

$0.500 	ext{ mol/L} 	imes 1.00 	ext{ L} 	imes 74.55 	ext{ g/mol} = 37.8 	ext{ g KCl}$

Question 10

A solution is prepared by adding 2.00 mL of a 1.00 M stock solution to a 25.0 mL volumetric flask and diluting to the line with water. What is the final concentration of the solution?

Accepted Answer

$M_2 = \frac{M_1V_1}{V_2} = \frac{1.00 	imes 2.00}{25.0} = 0.0800 	ext{ M}$

Question 11

Which of the following is the correct net ionic equation for the reaction between mercury(II) nitrate and potassium iodide?

Accepted Answer

$Hg^{2+}(aq) + 2I^-(aq) \rightarrow HgI_2(s)$

Question 12

Which of the following pairs of compounds will form a precipitate when mixed in aqueous solution?

Accepted Answer

NaCl and AgNO$_3$

Question 13

What is the correct formula for lead(II) acetate?

Accepted Answer

$Pb(C_2H_3O_2)_2$

Question 14

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

Accepted Answer

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

Question 15

A sample contains 5.8% $^{54}$Fe, 91.8% $^{56}$Fe, 2.1% $^{57}$Fe, and 0.28% $^{58}$Fe. What is the average atomic mass of iron?

Accepted Answer

$0.058 	imes 53.940 + 0.918 	imes 55.935 + 0.021 	imes 56.935 + 0.0028 	imes 57.933 = 55.87$

Question 16

Which of the following is the correct formula for perchlorate ion?

Accepted Answer

$ClO_4^-$

Question 17

Which of the following is a strong electrolyte?

Accepted Answer

NaCl (aq)

Question 18

Which of the following is the correct formula for sulfuric acid?

Accepted Answer

$H_2SO_4$

General Chemistry Exam 1 Study Guide: Atoms, Molecules, Stoichiometry, Solutions, and Nomenclature

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