Question 1

A 3.682-g sample of KClO₃ is dissolved in enough water to give 375. mL of solution. What is the chlorate ion concentration in this solution? A) 9.82 M B) 1.60 × 10^-1^M C) 8.01 ×10^-2^M D) 9.82 × 10^-3^M E) 1.60 × 10^-2^M

Accepted Answer

First, we need to determine the number of moles of KClO3 in the sample:

m(KClO3) = 3.682 g
M(KClO3) = 122.55 g/mol
n(KClO3) = m(KClO3) / M(KClO3) = 0.03 mol

Next, we need to determine the volume of the solution in liters:

V = 375 mL = 0.375 L

Finally, we can calculate the concentration of chlorate ions (ClO3-) using the following equation:

[ClO3-] = n(ClO3-) / V

Since KClO3 dissociates in water to produce one chlorate ion for every one KClO3 unit, the concentration of chlorate ions is equal to the concentration of KClO3:

[ClO3-] = [KClO3] = 0.03 mol / 0.375 L = 0.08 M = 8.01 × 10^-2 M

Therefore, the best choice is C.

Question 2

Vinegar is a solution of acetic acid, HC₂H₃O₂, dissolved in water. A 5.54-g sample of vinegar was neutralized by 30.10 mL of 0.100 M NaOH. What is the percent by weight of acetic acid in the vinegar? A) 0.0543% B) 1.08% C) 3.26% D) 5.43% E) 9.23%

Accepted Answer

First, we need to determine the moles of NaOH used:
30.10 mL x 0.100 mol NaOH/L = 0.003010 mol NaOH

Since we have a 1:1 stoichiometric ratio between NaOH and acetic acid, we know that the moles of acetic acid present in the vinegar is also 0.003010 mol.

Next, we can use the molecular weight of acetic acid (60.05 g/mol) to calculate the mass of acetic acid present in the sample:
0.003010 mol x 60.05 g/mol = 0.1809 g

Finally, we can calculate the percent by weight of acetic acid in the vinegar:
(0.1809 g / 5.54 g) x 100% = 3.26%

Therefore, the answer is choice C.

Question 3

What is the pH of a 0.056 M HNO₃ solution? A) 0.056 B) 1.25 C) 12.75 D) 2.88 E) 11.11

Accepted Answer

The answer of What is the pH of a 0.056...

Question 4

Balance the following oxidation-reduction equation: Li(s) + O₂(g) → Li₂O(s) A) 2Li(s) + O₂(g) → Li₂O(s) B) Li(s) + O₂(g) → Li₂O(s) C) 4Li(s) + O₂(g) → 2Li₂O(s) D) 2Li(s) + O₂(g) → 2Li₂O(s) E) 2Li(s) + O₂(g) → 4Li₂O(s)

Accepted Answer

The balanced equation requires 4 lithium atoms to react with 1 molecule of oxygen to form 2 formula units of lithium oxide.

Question 5

A 50.0 mL sample of 0.436 M NH₄NO₃ is diluted with water to a total volume of 250.0 mL. What is the ammonium nitrate concentration in the resulting solution? A) 2.18 M B) 0.523 M C) 0.349 M D) 0.174 M E) 0.0872 M

Accepted Answer

The concentration of ammonium nitrate after dilution can be calculated using the formula $C_1V_1 = C_2V_2$, where $C_1$ is the initial concentration, $V_1$ is the initial volume, $C_2$ is the final concentration, and $V_2$ is the final volume. Plugging in the given values: $0.436 \, \text{M} \times 50.0 \, \text{mL} = C_2 \times 250.0 \, \text{mL}$. Solving for $C_2$ gives $C_2 = 0.0872 \, \text{M}$.

Question 6

Automobile batteries use 3.0 M H₂SO₄ as an electrolyte. How much 1.20 M NaOH will be needed to neutralize 225 mL of battery acid? H₂SO₄(aq) + 2NaOH(aq) → 2H₂O(l) + Na₂SO₄(aq) A) 0.045 L B) 0.28 L C) 0.56 L D) 0.90 L E) 1.1 L

Accepted Answer

The answer of Automobile batteries use 3.0 M H₂SO₄ as...

Question 7

Starting with a 1.35 M HCl stock solution, five standard solutions are prepared by sequentially diluting 5.00 mL of each solution to 100.0 mL. What is the concentration of the final solution? A) 3.38 × 10^-3^M B) 1.69 × 10^-4^M C) 6.25 × 10^-2^M D) 4.22 × 10^-7^M E) 1.35 M

Accepted Answer

Each dilution reduces the concentration by a factor of 20 (5.00 mL to 100.0 mL). After five dilutions, the concentration is (1.35 M) / (20^5) = 4.22 × 10^-7 M.

Question 8

A 0.8838-g sample of an ionic compound containing bromide ions and an unknown metal cation is dissolved in water and treated with an excess of AgNO₃. If 1.573 g of a AgBr precipitate forms, what is the percent by mass of Br in the original compound? A) 62.13% B) 75.72% C) 56.19% D) 42.55% E) 37.87%

Accepted Answer

First, we need to determine how many moles of AgBr were formed in the reaction:
moles of AgBr = mass / molar mass = 1.573 g / (107.87 g/mol) = 0.0146 mol AgBr

Since AgBr is a 1:1 ratio compound, we know that moles of AgBr = moles of Br in the original compound.

Next, we can use the mass of the original compound and the moles of Br to find the percent by mass of Br:
moles of Br = 0.0146 mol AgBr
mass of original compound = 0.8838 g

mass percent of Br = (moles of Br x molar mass of Br / mass of original compound) x 100%
mass percent of Br = (0.0146 mol x 79.90 g/mol / 0.8838 g) x 100%
mass percent of Br = 75.72%

Therefore, the answer is B) 75.72%.

Question 9

A 4.691-g sample of MgCl₂ is dissolved in enough water to give 750. mL of solution. What is the magnesium ion concentration in this solution? A) 6.25 M B) 6.57 × 10^-2^M C) 4.38 × 10^-2^M D) 3.29 × 10^-2^M E) 2.19 ×10^-2^M

Accepted Answer

The molecular weight of MgCl2 is approximately 95.21 g/mol (24.31 g/mol for Mg + 2*(35.45 g/mol) for Cl). The number of moles of MgCl2 in a 4.691-g sample is calculated by dividing the mass of the sample by the molar mass of MgCl2: 4.691 g / 95.21 g/mol = 0.04927 mol. The concentration of magnesium ions is then the number of moles of MgCl2 divided by the volume of the solution in liters: 0.04927 mol / 0.750 L = 0.0657 mol/L or 6.57 × 10^-2 M.

Question 10

Identify the oxidizing agent in the chemical reaction 2MnO₄^- + 5H₂SO₃→ 2Mn²⁺ + 5SO₄^2-+ 4H⁺ + 3H₂O. A) MnO₄^- B) H₂SO₃ C) Mn²⁺ D) SO₄^2- E) H⁺

Accepted Answer

MnO₄^- is the oxidizing agent because it undergoes reduction, losing electrons and causing the oxidation of H₂SO₃.

Question 11

Identify the reducing agent in the chemical reaction Cd + NiO₂ + 2H₂O → Cd(OH)₂ + Ni(OH)₂ A) Cd B) NiO₂ C) H₂O D) Cd(OH)₂ E) Ni(OH)₂

Accepted Answer

The reducing agent in a chemical reaction is the substance that donates electrons and becomes oxidized. In the given reaction, Cd is oxidized and loses electrons, therefore it is the reducing agent.

Question 12

What mass of lithium phosphate is needed to prepare 500. mL of a solution having a lithium ion concentration of 0.125 M?
A) 2.41 g
B) 7.24 g
C) 14.5 g
D) 21.7 g
E) 43.4 g

Accepted Answer

The molar mass of lithium phosphate is 115.79 g/mol. The number of moles of lithium ions in 500. mL of a 0.125 M solution is:$$0.125 	ext{ mol/L} 	imes 0.500 	ext{ L} = 0.0625 	ext{ mol}$$The number of moles of lithium phosphate needed to provide this number of lithium ions is also 0.0625 mol. The mass of lithium phosphate needed is:$$0.0625 	ext{ mol} 	imes 115.79 	ext{ g/mol} = 7.24 	ext{ g}$$

Question 13

What is the reducing agent in the following reaction? 5Fe²⁺(aq) + MnO₄^-(aq) + 8H⁺(aq) → 5Fe³⁺(aq) + Mn²⁺(aq) + 4H₂O(l) A) Fe²⁺ B) MnO₄^- C) H⁺ D) Mn²⁺ E) Fe³⁺

Accepted Answer

FeS2 (iron(II) disulfide) acts as the reducing agent because it loses electrons, going from Fe(II) in FeS2 to Fe(III) in Fe2(SO4)3, indicating it has been oxidized.

Question 14

35.0 mL of 0.255 M nitric acid is added to 45.0 mL of 0.328 M Mg(NO₃)₂. What is the concentration of nitrate ion in the final solution? A) 0.296 M B) 0.481 M C) 0.583 M D) 0.911 M E) 0.148 M

Accepted Answer

The answer of 35.0 mL of 0.255 M nitric acid...

Question 15

Which is a correct description of the following reaction? H₂SO₄ + Cd(OH)₂→ 2H₂O + CdSO₄ A) This reaction is an acid-base reaction. B) In this reaction, hydrogen is oxidized. C) In this reaction, sulfur is oxidized. D) In this reaction, cadmium is oxidized. E) In this reaction, oxygen is oxidized.

Accepted Answer

This reaction is an example of an acid-base reaction, where the hydroxide ion (OH-) from cadmium hydroxide (Cd(OH)2) reacts with the hydrogen ion (H+) from the acid (H2SO4) to form water (H2O), and the sulfate ion (SO42-) from the acid reacts with cadmium (Cd2+) to form cadmium sulfate (CdSO4).

Question 16

How many sodium ions are present in 325 mL of 0.850 M Na₂SO₄? A) 5.12 × 10²³ Na ions B) 8.32 × 10²² Na ions C) 1.02 × 10²⁴ Na ions D) 1.66 × 10²³ Na ions E) 3.33 × 10²³ Na ions

Accepted Answer

The answer of How many sodium ions are present in...

Question 17

In the reaction 5H₂O₂ + 2MnO₄^-+ 6H⁺→ 2Mn²⁺ + 8H₂O + 5O₂, what is the oxidizing agent? A) H₂O₂ B) MnO₄^- C) H⁺ D) Mn²⁺ E) O₂

Accepted Answer

The oxidizing agent is the species that gets reduced, meaning it loses electrons. In this reaction, MnOS1U1B14S1U1B0S1U1P1-S1S1P0 gets reduced to MnS1U1P12, which means it is the oxidizing agent.

Question 18

Which element is reduced in the following reaction? Cu + 2H₂SO₄→ CuSO₄ + SO₂ + 2H₂O A) Cu B) H C) S D) O E) H₂O

Accepted Answer

In the given reaction, sulfur (S) undergoes a decrease in oxidation state from +6 in $SO_4^{2-}$ to -2 in $CuS$, indicating it is reduced.

Question 19

A standard solution of 0.243 M NaOH was used to determine the concentration of a hydrochloric acid solution. If 46.33 mL of NaOH is needed to neutralize 10.00 mL of the acid, what is the molar concentration of the acid in the original solution?
A) 0.243 M
B) 0.200 M
C) 1.13 M
D) 0.563 M
E) 0.0313 M

Accepted Answer

First, we need to determine the moles of NaOH used:
moles NaOH = M NaOH x L NaOH
moles NaOH = 0.243 M x 0.04633 L
moles NaOH = 0.01122719 mol

Since the reaction is a 1:1 ratio of acid to base, this means that the molarity of the acid is also 0.01122719 mol/L.

Now, we need to calculate the molarity of the acid in the original solution. To do this, we use the formula:
M1V1 = M2V2

where M1 is the molarity of the NaOH solution, V1 is the volume of NaOH used, M2 is the molarity of the acid, and V2 is the volume of the acid used.

Plugging in the values we know:
(0.243 M)(0.04633 L) = M2(0.01000 L)
M2 = 1.11983 mol/L = 1.13 M

Therefore, the molar concentration of the acid in the original solution is 1.13 M.

Question 20

How many moles of H⁺(aq) ions are present in 750 mL of 0.65 M hydrochloric acid? A) 1.2 mol B) 0.98 mol C) 0.87 mol D) 0.65 mol E) 0.49 mol

Accepted Answer

The number of moles of H⁺ ions in the solution can be calculated using the formula: moles = molarity × volume (in liters). For 0.65 M HCl, the calculation is 0.65 moles/L × 0.75 L = 0.4875 moles, which rounds to 0.49 moles.

Quiz 4: Reactions in Aqueous Solutions

A 3.682-g sample of KClO₃ is dissolved in enough water to give 375. mL of solution. What is the chlorate ion concentration in this solution?

Vinegar is a solution of acetic acid, HC₂H₃O₂, dissolved in water. A 5.54-g sample of vinegar was neutralized by 30.10 mL of 0.100 M NaOH. What is the percent by weight of acetic acid in the vinegar?

What is the pH of a 0.056 M HNO₃ solution?

Balance the following oxidation-reduction equation: Li(s) + O₂(g) → Li₂O(s)

A 50.0 mL sample of 0.436 M NH₄NO₃ is diluted with water to a total volume of 250.0 mL. What is the ammonium nitrate concentration in the resulting solution?

Automobile batteries use 3.0 M H₂SO₄ as an electrolyte. How much 1.20 M NaOH will be needed to neutralize 225 mL of battery acid? H₂SO₄(aq) + 2NaOH(aq) → 2H₂O(l) + Na₂SO₄(aq)

Starting with a 1.35 M HCl stock solution, five standard solutions are prepared by sequentially diluting 5.00 mL of each solution to 100.0 mL. What is the concentration of the final solution?

A 0.8838-g sample of an ionic compound containing bromide ions and an unknown metal cation is dissolved in water and treated with an excess of AgNO₃. If 1.573 g of a AgBr precipitate forms, what is the percent by mass of Br in the original compound?

A 4.691-g sample of MgCl₂ is dissolved in enough water to give 750. mL of solution. What is the magnesium ion concentration in this solution?

Identify the oxidizing agent in the chemical reaction 2MnO₄^- + 5H₂SO₃→ 2Mn²⁺ + 5SO₄^2-+ 4H⁺ + 3H₂O.

Identify the reducing agent in the chemical reaction Cd + NiO₂ + 2H₂O → Cd(OH) ₂ + Ni(OH) ₂

What mass of lithium phosphate is needed to prepare 500. mL of a solution having a lithium ion concentration of 0.125 M?

What is the reducing agent in the following reaction? 5Fe²⁺(aq) + MnO₄^-(aq) + 8H⁺(aq) → 5Fe³⁺(aq) + Mn²⁺(aq) + 4H₂O(l)

35.0 mL of 0.255 M nitric acid is added to 45.0 mL of 0.328 M Mg(NO₃) ₂. What is the concentration of nitrate ion in the final solution?

Which is a correct description of the following reaction? H₂SO₄ + Cd(OH) ₂→ 2H₂O + CdSO₄

How many sodium ions are present in 325 mL of 0.850 M Na₂SO₄?

In the reaction 5H₂O₂ + 2MnO₄^-+ 6H⁺→ 2Mn²⁺ + 8H₂O + 5O₂, what is the oxidizing agent?

Which element is reduced in the following reaction? Cu + 2H₂SO₄→ CuSO₄ + SO₂ + 2H₂O

A standard solution of 0.243 M NaOH was used to determine the concentration of a hydrochloric acid solution. If 46.33 mL of NaOH is needed to neutralize 10.00 mL of the acid, what is the molar concentration of the acid in the original solution?

How many moles of H⁺(aq) ions are present in 750 mL of 0.65 M hydrochloric acid?

Quiz 4: Reactions in Aqueous Solutions

A 3.682-g sample of KClO3 is dissolved in enough water to give 375. mL of solution. What is the chlorate ion concentration in this solution?

Vinegar is a solution of acetic acid, HC2H3O2, dissolved in water. A 5.54-g sample of vinegar was neutralized by 30.10 mL of 0.100 M NaOH. What is the percent by weight of acetic acid in the vinegar?

What is the pH of a 0.056 M HNO3 solution?

Balance the following oxidation-reduction equation: Li(s) + O2(g) → Li2O(s)

A 50.0 mL sample of 0.436 M NH4NO3 is diluted with water to a total volume of 250.0 mL. What is the ammonium nitrate concentration in the resulting solution?

Automobile batteries use 3.0 M H2SO4 as an electrolyte. How much 1.20 M NaOH will be needed to neutralize 225 mL of battery acid? H2SO4(aq) + 2NaOH(aq) → 2H2O(l) + Na2SO4(aq)

Starting with a 1.35 M HCl stock solution, five standard solutions are prepared by sequentially diluting 5.00 mL of each solution to 100.0 mL. What is the concentration of the final solution?

A 0.8838-g sample of an ionic compound containing bromide ions and an unknown metal cation is dissolved in water and treated with an excess of AgNO3. If 1.573 g of a AgBr precipitate forms, what is the percent by mass of Br in the original compound?

A 4.691-g sample of MgCl2 is dissolved in enough water to give 750. mL of solution. What is the magnesium ion concentration in this solution?

Identify the oxidizing agent in the chemical reaction 2MnO4- + 5H2SO3→ 2Mn2+ + 5SO42- + 4H+ + 3H2O.

Identify the reducing agent in the chemical reaction Cd + NiO2 + 2H2O → Cd(OH) 2 + Ni(OH) 2