Question 1

In a qualitative cation analysis,the unknown ion is unaffected by HCl(aq),but is precipitated by aqueous hydrogen sulfide.The unknown ion is ________. A)NH₄⁺ B)Cu²⁺ C)Ag⁺ D)K⁺ E)Na⁺

Accepted Answer

In qualitative cation analysis, ions that are precipitated by aqueous hydrogen sulfide in the presence of hydrochloric acid belong to the second analytical group of cations. Copper (Cu^2+) is a classic example of such an ion, as it forms a precipitate with H2S in acidic conditions, unlike the ions that are unaffected or form soluble compounds under these conditions.

Question 2

What is the minimum pH at which cobalt(II)hydroxide (K_sp = 2.0 × 10^-16)will precipitate from an aqueous solution of 0.020 M in Co²⁺? A)5.8 B)6.2 C)7.0 D)7.8 E)8.2

Accepted Answer

The answer of What is the minimum pH at which...

Question 3

What is the molar solubility of Mg(OH)₂(s)in a basic aqueous solution with a pH of 12.50? K_spfor Mg(OH)₂(s)is A)1.8 × 10^-¹⁰ mol L^-1 B)5.6 × 10^-⁹ mol L^-1 C)2.4 × 10^-6 mol L^-1 D)1.1 × 10^-4 mol L^-1

Accepted Answer

The answer of What is the molar solubility of Mg(OH)₂(s)in...

Question 4

To a concentrated buffer of pH 4.0 is added an equal volume of an aqueous solution that is 0.020 M in Cr³⁺,Cd²⁺ and Al³⁺.The expected precipitate would consist of ________. A)Al(OH)₃ B)Al(OH)₃ and Cr(OH)₃ C)Cd(OH)₂ D)Cd(OH)₂ and Cr(OH)₃ E)Cd(OH)₂,Cr(OH)₃ and Al(OH)₃

Accepted Answer

The answer of To a concentrated buffer of pH 4.0...

Question 5

An aqueous solution contains [Ba²⁺] = 5.0 × 10^-5 M,[Ag⁺] = 3.0 × 10^-5 M,and [Zn²⁺] = 2.0 × 10^-7 M.Sodium oxalate is slowly added so that [C₂O₄^2-] increases. Which one of the oxalates precipitates first? A)BaC₂O₄ B)Na₂C₂O₄ C)ZnC₂O₄ D)Ag₂C₂O₄ E)ZnC₂O₄ and Ag₂C₂O₄precipitate together

Accepted Answer

The answer of An aqueous solution contains [Ba²⁺] = 5.0...

Question 6

In a qualitative cation analysis,the unknown ion is not precipitated by aqueous solutions of HCl(aq),H₂S(aq),or CO₃^2-(aq).A flame test produced a violet flame.The unknown ion is ________. A)Ag⁺ B)Pb²⁺ C)Fe²⁺ D)K⁺ E)NH⁴⁺

Accepted Answer

The violet flame test result is characteristic of potassium ions (K+), indicating that the unknown ion is potassium.

Question 7

Concentrated aqueous solutions of sodium sulfate,ammonium carbonate,and nickel (II)nitrate are mixed together.The precipitate which forms is ________.
A)nickel (II)carbonate
B)nickel (II)sulfate
C)sodium carbonate
D)ammonium sulfate
E)nothing precipitates

Accepted Answer

When aqueous solutions of sodium sulfate and nickel (II) nitrate are mixed together, they will react to form nickel (II) sulfate and sodium nitrate which will remain in solution.

Na2SO4 + Ni(NO3)2 -> NiSO4 + 2NaNO3

When ammonium carbonate is added to the solution, it will react with nickel (II) sulfate to form nickel (II) carbonate, ammonium sulfate, and water.

NiSO4 + (NH4)2CO3 -> NiCO3 + (NH4)2SO4 + H2O

The nickel (II) carbonate formed will precipitate out of solution, leaving ammonium sulfate and sodium nitrate in solution. Therefore, the precipitate which forms is nickel (II) carbonate (choice A).

Question 8

What is the molar solubility of barium fluoride ( BaF₂ )in water? The solubility-product constant for BaF₂ (s)is 1.7 × 10^-6 at A)6.5 × 10^-4 mol L^-1 B)1.2 × 10^-2 mol L^-1 C)1.8 × 10^-3 mol L^-1 D)7.5 × 10^-3 mol L^-1 E)5.7 × 10^-7 mol L^-1

Accepted Answer

The answer of What is the molar solubility of barium...

Question 9

Calculate the solubility (in g L^-1)of calcium fluoride in water at 25 °C if the K_sp for CaF₂ Is 1.5 × 10^-10 A)9.6 × 10^-4 g L^-1 B)2.6 × 10^-2 g L^-1 C)3.3 × 10^-2 g L^-1 D)4.1 × 10^-2 g L^-1

Accepted Answer

The solubility product expression for CaF2 is Ksp = [Ca2+][F-]^2. Let the solubility of CaF2 be s mol/L. Then, [Ca2+] = s and [F-] = 2s. Substituting these into the Ksp expression gives 1.5 × 10^-10 = s(2s)^2 = 4s^3. Solving for s gives s = 3.3 × 10^-4 mol/L. The molar mass of CaF2 is approximately 78.08 g/mol, so the solubility in g/L is 3.3 × 10^-4 mol/L × 78.08 g/mol = 2.6 × 10^-2 g/L.

Question 10

Concentrated aqueous solutions of iron (III)chloride,sodium hydroxide,and potassium nitrate are mixed together.The precipitate which forms is ________.
A)potassium hydroxide
B)sodium chloride
C)iron (III)hydroxide
D)iron (III)nitrate
E)nothing precipitates

Accepted Answer

Iron (III) chloride reacts with sodium hydroxide to form a precipitate of iron (III) hydroxide, which can be represented by the following equation:
FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl
Potassium nitrate does not react with either iron (III) chloride or sodium hydroxide, so it remains in solution. Thus, the precipitate which forms is iron (III) hydroxide.

Question 11

In which of the following aqueous solutions would solid AgCl be expected to be the least soluble at 25 °C? A)0.1 mol L^-1 HCl B)0.1 mol L^-1 KCl C)0.1 mol L^-1 BaCl₂ D)0.1 mol L^-1 KNO₃

Accepted Answer

According to the solubility rules, AgCl is insoluble in solutions containing Cl- ions and slightly soluble in solutions containing NO3- ions. Therefore, the least soluble solution would be the one with an ion that does not form a soluble compound with Ag+ or Cl-. BaCl₂ is the only option that fits this criteria, as BaAgCl_{2 and BaCl2} are both insoluble.

Question 12

Calculate the molar solubility of thallium chloride (TlCl)in 0.30 mol L^-1 NaCl(aq)at 25 °C.K_sp for TlCl(s)is A)5.1 × 10^-5 mol L^-1 B)5.7 × 10^-⁴ mol L^-1 C)7.1 × 10^-3 mol L^-1 D)1.3 × 10^-2 mol L^-1

Accepted Answer

We can use the following equation to calculate the molar solubility of TlCl:

Ksp = [Tl+][Cl-]

Let x be the molar solubility of TlCl, then we have:

Ksp = (x)(x) = x^2

Since we are given the concentration of NaCl, we can assume that the ionization of TlCl is negligible compared to NaCl, therefore [Na+] is approximately equal to [Cl-]. We can use the concentration of NaCl as the concentration of Cl-:

[Cl-] = 0.30 mol L-1

Substituting the values into the equation for Ksp, we get:

11ea7a5e_3e74_11f5_89bd_dfb3f1da36a5_TB5343_11 = x^2

x = 5.7 × 10-15 mol L-1

Therefore, the correct answer is B.

Question 13

In a qualitative cation analysis,the unknown ion is not precipitated by HCl or H₂S,but is precipitated by CO₃^2-.The unknown ion is ________. A)Ag⁺ B)Mn²⁺ C)Ca²⁺ D)K⁺ E)Al³⁺

Accepted Answer

Calcium ions (Ca²⁺) are not precipitated by HCl or H₂S, but they form a precipitate with carbonate ions (CO₃^2-) as calcium carbonate (CaCO₃).

Question 14

What ratio of [NH₄⁺]/[NH₃] would provide a buffer of pH low enough to avoid precipitation of Co(OH)₂(s)from a 0.50 M Co²⁺(aq)solution? (K_b for NH₃ = 1.8 × 10^-5 and K_{sp for} Co(OH)₂= 2.0 × 10^-14 A)1/50 B)1/90 C)1/1 D)90/1 E)50/1

Accepted Answer

To avoid the precipitation of Co(OH)₂ from a Co²⁺ solution, the pH must be kept low enough to prevent reaching the solubility product (K_sp) of Co(OH)₂. The buffer system NH₄⁺/NH₃ (ammonium/ammonia) can be used to control the pH. The K_a for NH₄⁺ is 1.8 × 10⁻⁵, which corresponds to a pK_a of -log(1.8 × 10⁻⁵) ≈ 4.74. To prevent Co(OH)₂ precipitation, the pH should be lower than the pOH at which Co(OH)₂ would precipitate. The K_sp for Co(OH)₂ is 2.0 × 10⁻¹⁴, and since Co(OH)₂ dissociates into Co²⁺ and 2 OH⁻, we can set up the equation K_sp = [Co²⁺][OH⁻]². Given a 0.50 M Co²⁺ solution, and assuming complete dissociation for simplicity, the concentration of OH⁻ needed to reach the K_sp can be calculated. However, without precise calculations, we know we need to shift the equilibrium of the NH₄⁺/NH₃ buffer towards NH₄⁺ to lower the pH. This requires a high ratio of NH₄⁺ (acidic component) to NH₃ (basic component), which corresponds to option D, 90/1. This high ratio ensures the solution remains acidic enough to prevent Co(OH)₂ precipitation by keeping the concentration of OH⁻ ions low.

Question 15

Concentrated aqueous solutions of copper (I)nitrate,sodium sulfate and silver acetate are mixed together.The precipitate which forms is ________.
A)copper (I)acetate
B)silver nitrate
C)silver sulfate
D)sodium acetate
E)nothing precipitates

Accepted Answer

When copper (I) nitrate and sodium sulfate are mixed, no precipitate is expected as both compounds are soluble in water. However, when silver acetate is added to the mixture, a precipitation reaction occurs as silver acetate is insoluble in water.

The balanced chemical equation for the reaction is:

2AgCH3COO (aq) + Cu2(NO3)2 (aq) + Na2SO4 (aq) → Cu(CH3COO)2 (s) + 2AgNO3 (aq) + Na2(CH3COO)2 (aq) + SO4 (aq)

The solid formed is copper (I) acetate (Cu(CH3COO)2), which is a yellowish-green color. Therefore, the best choice is C), silver sulfate is not formed during this reaction.

Question 16

Saturated aqueous solutions of sodium sulfate,ammonium carbonate,and nickel (II)nitrate are mixed together.The precipitate that forms is ________.
A)nickel (II)carbonate
B)sodium carbonate
C)nickel (II)sulfate
D)ammonium sulfate
E)sodium nitrate

Accepted Answer

When sodium sulfate and nickel (II) nitrate are mixed, no precipitate forms because both salts are soluble in water. However, when ammonium carbonate is added, it reacts with sodium sulfate to form ammonium sulfate and sodium carbonate, both of which are soluble in water. The nickel (II) ion then reacts with carbonate ion to form a solid precipitate of nickel (II) carbonate, which is insoluble in water. Therefore, the answer is A) nickel (II) carbonate.

Question 17

What is the molar solubility of manganese carbonate ( MnCO₃ )in water? The solubility-product constant for MnCO₃ (s)is 5.0 × 10^-10 at 25 °C. A)2.5 × 10^-10 mol L^-1 B)1.0 × 10^-9 mol L^-1 C)9.3 mol L^-1 D)3.2 × 10^-5 mol L^-1 E)2.2 × 10^-5 mol L^-1

Accepted Answer

The molar solubility of MnCO₃ can be calculated using the solubility product constant (Ksp). For MnCO₃, Ksp = [Mn²⁺][CO₃²⁻] = s², where s is the molar solubility. Solving s² = 5.0 × 10⁻¹⁰ gives s = √(5.0 × 10⁻¹⁰) = 2.2 × 10⁻⁵ mol L⁻¹.

Question 18

In a qualitative cation analysis,the unknown ion is precipitated by HCl(aq),remains as a chloride solid in hot water,and the precipitate turns black upon addition of aqueous ammonia.The unknown ion is ________. A)Hg₂²⁺ B)Pb²⁺ C)Ag⁺ D)K⁺ E)Cd²⁺

Accepted Answer

The unknown ion is Hg2+ because it forms a precipitate with HCl, which does not dissolve in hot water, and turns black upon addition of aqueous ammonia, indicating the formation of a mercury-ammonia complex.

Question 19

A swimming pool was sufficiently alkaline so that the carbon dioxide absorbed from the air produced a solution in the pool that was 2 × 10^-4 M in carbonate ion.If the pool originally contained 4 × 10^-3 M Mg²⁺,6 × 10^-4 M Ca²⁺,and 8 × 10^-7 M Fe²⁺,then the precipitate that was formed consisted of ________. (K_sp values are: CaCO₃,4.7 × 10^-9;MgCO₃,4.0 × 10^-5;FeCO₃,2.0 × 10^-11) A)only MgCO₃ B)only CaCO₃ C)only FeCO₃ D)only CaCO₃ and FeCO₃ E)MgCO₃,CaCO₃,and FeCO₃

Accepted Answer

The question states that the pool is sufficiently alkaline to have a concentration of 2 × 10^-4 M carbonate ion. This concentration is greater than the solubility product for MgCO3 (4.0 × 10^-5) but less than the solubility product for CaCO3 (4.7 × 10^-9) and FeCO3 (2.0 × 10^-11). Therefore, MgCO3 will not precipitate, but both CaCO3 and FeCO3 will precipitate. Thus, the precipitate will consist of CaCO3 and FeCO3, making the correct answer choice D.

Question 20

Calculate the K_sp for silver carbonate if the solubility of Ag₂CO₃(s)in pure water is 3.5 × 10^-2g L^-1. A)1.3 × 10^-4 B)8.4 × 10^-12 C)4.6 × 10^-7 D)5.8 × 10^-10

Accepted Answer

Silver carbonate ($Ag_2CO_3$) dissociates in water according to the equation: $Ag_2CO_3(s) \rightarrow 2Ag^+(aq) + CO_3^{2-}(aq)$. Given the solubility of $Ag_2CO_3$ is $3.5 \times 10^{-2}$ g/L, we first convert this to moles/L (molarity, M) using its molar mass ($M_{Ag_2CO_3} = 275.75$ g/mol). Solubility in moles/L: $\frac{3.5 \times 10^{-2}\, \text{g/L}}{275.75\, \text{g/mol}} = 1.27 \times 10^{-4}\, \text{M}$.For every mole of $Ag_2CO_3$ that dissolves, 2 moles of $Ag^+$ and 1 mole of $CO_3^{2-}$ are produced. Therefore, the concentration of $Ag^+$ is $2 \times 1.27 \times 10^{-4} = 2.54 \times 10^{-4}\, \text{M}$, and the concentration of $CO_3^{2-}$ is $1.27 \times 10^{-4}\, \text{M}$.The $K_{sp}$ for $Ag_2CO_3$ is calculated as: $K_{sp} = [Ag^+]^2[CO_3^{2-}]$.Substituting the concentrations: $K_{sp} = (2.54 \times 10^{-4})^2 \times 1.27 \times 10^{-4} = 8.2 \times 10^{-12}$.The closest answer choice to this calculated value is $8.4 \times 10^{-12}$, which is option B.

Quiz 18: Solubility and Complex-Ion Equilibria

In a qualitative cation analysis,the unknown ion is unaffected by HCl(aq) ,but is precipitated by aqueous hydrogen sulfide.The unknown ion is ________.

What is the minimum pH at which cobalt(II) hydroxide (K_sp = 2.0 × 10^-16) will precipitate from an aqueous solution of 0.020 M in Co²⁺?

What is the molar solubility of Mg(OH) ₂(s) in a basic aqueous solution with a pH of 12.50? K_spfor Mg(OH) ₂(s) is

To a concentrated buffer of pH 4.0 is added an equal volume of an aqueous solution that is 0.020 M in Cr³⁺,Cd²⁺ and Al³⁺.The expected precipitate would consist of ________.

An aqueous solution contains [Ba²⁺] = 5.0 × 10^-5 M,[Ag⁺] = 3.0 × 10^-5 M,and [Zn²⁺] = 2.0 × 10^-7 M.Sodium oxalate is slowly added so that [C₂O₄^2-] increases. Which one of the oxalates precipitates first?

In a qualitative cation analysis,the unknown ion is not precipitated by aqueous solutions of HCl(aq) ,H₂S(aq) ,or CO₃^2-(aq) .A flame test produced a violet flame.The unknown ion is ________.

Concentrated aqueous solutions of sodium sulfate,ammonium carbonate,and nickel (II) nitrate are mixed together.The precipitate which forms is ________.

What is the molar solubility of barium fluoride ( BaF₂ ) in water? The solubility-product constant for BaF₂ (s) is 1.7 × 10^-6 at

Calculate the solubility (in g L^-1) of calcium fluoride in water at 25 °C if the K_sp for CaF₂ Is 1.5 × 10^-10

Concentrated aqueous solutions of iron (III) chloride,sodium hydroxide,and potassium nitrate are mixed together.The precipitate which forms is ________.

In which of the following aqueous solutions would solid AgCl be expected to be the least soluble at 25 °C?

Calculate the molar solubility of thallium chloride (TlCl) in 0.30 mol L^-1 NaCl(aq) at 25 °C.K_sp for TlCl(s) is

In a qualitative cation analysis,the unknown ion is not precipitated by HCl or H₂S,but is precipitated by CO₃^2-.The unknown ion is ________.

What ratio of [NH₄⁺]/[NH₃] would provide a buffer of pH low enough to avoid precipitation of Co(OH) ₂(s) from a 0.50 M Co²⁺(aq) solution? (K_b for NH₃ = 1.8 × 10^-5 and K_{sp for} Co(OH) ₂= 2.0 × 10^-14

Concentrated aqueous solutions of copper (I) nitrate,sodium sulfate and silver acetate are mixed together.The precipitate which forms is ________.

Saturated aqueous solutions of sodium sulfate,ammonium carbonate,and nickel (II) nitrate are mixed together.The precipitate that forms is ________.

What is the molar solubility of manganese carbonate ( MnCO₃ ) in water? The solubility-product constant for MnCO₃ (s) is 5.0 × 10^-10 at 25 °C.

In a qualitative cation analysis,the unknown ion is precipitated by HCl(aq) ,remains as a chloride solid in hot water,and the precipitate turns black upon addition of aqueous ammonia.The unknown ion is ________.

Calculate the K_sp for silver carbonate if the solubility of Ag₂CO₃(s) in pure water is 3.5 × 10^-2g L^-1.

Quiz 18: Solubility and Complex-Ion Equilibria

In a qualitative cation analysis,the unknown ion is unaffected by HCl(aq) ,but is precipitated by aqueous hydrogen sulfide.The unknown ion is ________.

What is the minimum pH at which cobalt(II) hydroxide (Ksp = 2.0 × 10-16) will precipitate from an aqueous solution of 0.020 M in Co2+?

What is the molar solubility of Mg(OH) 2(s) in a basic aqueous solution with a pH of 12.50? Ksp for Mg(OH) 2(s) is

To a concentrated buffer of pH 4.0 is added an equal volume of an aqueous solution that is 0.020 M in Cr3+,Cd2+ and Al3+.The expected precipitate would consist of ________.

An aqueous solution contains [Ba2+] = 5.0 × 10-5 M,[Ag+] = 3.0 × 10-5 M,and [Zn2+] = 2.0 × 10-7 M.Sodium oxalate is slowly added so that [C2O42-] increases. Which one of the oxalates precipitates first?

In a qualitative cation analysis,the unknown ion is not precipitated by aqueous solutions of HCl(aq) ,H2S(aq) ,or CO32-(aq) .A flame test produced a violet flame.The unknown ion is ________.