List of practice Questions

The concentration of sulphide ion in 0.1M HCl solution saturated with hydrogen sulphide is 1.0 × 10^–19 M. If 10 mL of this is added to 5 mL of 0.04 M solution of the following: FeSO₄, MnCl₂, ZnCl2 and CdCl₂. in which of these solutions precipitation will take place?

At 700 K, equilibrium constant for the reaction:
\(H_2 (g) + I_2 (g) ⇋ 2HI (g)\)
is 54.8. If 0.5 mol L^–1 of HI(g) is present at equilibrium at 700 K, what are the concentration of H₂(g) and I₂(g) assuming that we initially started with HI(g) and allowed it to reach equilibrium at 700 K?

What is K_c for the following equilibrium when the equilibrium concentration of each substance is: [SO₂]= 0.60 M, [O₂] = 0.82 M and [SO₃] = 1.90 M ?
\(2SO_2(g) + O_2(g) ⇋ 2SO_3(g)\)

Write the expression for the equilibrium constant, K_c for each of the following reactions: 

1. \(2NOCl (g) ⇋ 2NO (g) + Cl_2 (g)\)
2. \(2Cu(NO_3)_2 (s) ⇋ 2CuO (s) + 4NO_2 (g) + O_2 (g)\)
3. \(CH_3COOC_2H_5(aq) + H_2O(l) ⇋ CH_3COOH (aq) + C_2H_5OH (aq)\)
4. \(Fe^{3+} (aq) + 3OH^– (aq) ⇋ Fe(OH)_3 (s)\)
5. \(I_2 (s) + 5F_2 ⇋ 2IF_5\)

Find out the value of \(K_c\) for each of the following equilibria from the value of \(K_p\): 

1. \(2NOCl (g) ⇋ 2NO (g) + Cl_2 (g); \ K_p= 1.8 × 10^{–2}\  at \ 500\ K\)
2. \(CaCO_3 (s) ⇋ CaO(s) + CO_2(g); \ K_p= 167 \ at \ 1073\  K\)

For the following equilibrium, \(K_c = 6.3 × 10^{14}\) at \(1000\  K\)
\(NO (g) + O_3 (g) ⇋ NO_2 (g) + O_2 (g)\)
Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is \(K'_c\) for the reverse reaction?

Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

Reaction between \(N_2\) and \(O_2^–\) takes place as follows: 
\(2N_2 (g) + O_2 (g) ⇋ 2N_2O (g)\)
If a mixture of \(0.482 \ mol\) \(N_2\) and \(0.933\  mol\) of \(O_2\) is placed in a \(10\  L\) reaction vessel and allowed to form \(N_2O\) at a temperature for which \(K_c = 2.0 × 10^{–37}\), determine the composition of equilibrium mixture.

Nitric oxide reacts with Br₂ and gives nitrosyl bromide as per reaction given below:
\(2NO (g) + Br_2 (g) ⇋ 2NOBr (g)\)
When 0.087 mol of NO and 0.0437 mol of Br₂ are mixed in a closed container at constant temperature, 0.0518 mol of NOBr is obtained at equilibrium. Calculate equilibrium amount of NO and Br₂ .

At \(450\ K\), \(K_p= 2.0 × 10^{10}/bar\) for the given reaction at equilibrium.
\(2SO_2(g) + O_2(g) ⇋ 2SO_3 (g)\)
What is \(K_c\) at this temperature ?

What is the minimum volume of water required to dissolve 1g of calcium sulfate at 298 K? (For calcium sulfate, K_sp is 9.1 × 10^–6).

What is the maximum concentration of equimolar solutions of ferrous sulphate and sodium sulphide so that when mixed in equal volumes, there is no precipitation of iron sulphide? (For iron sulphide, Ksp = 6.3 × 10^–18).

Equal volumes of 0.002 M solutions of sodium iodate and cupric chlorate are mixed. Will it lead to the precipitation of copper iodate? (For cupric iodate K_sp = 7.4 × 10^–8).

The equilibrium constant expression for a gas reaction is, 
\(K_c = \frac {[NH_3]^4 [O_2]^5 }{[NO_4] [H_2O_6]}\)
Write the balanced chemical equation corresponding to this expression.

One mole of H₂O and one mole of CO are taken in 10 L vessel and heated to 725 K. At equilibrium 40% of water (by mass) reacts with CO according to the equation,
\(H_2O (g) + CO (g) ⇋ H_2 (g) + CO_2 (g)\)
Calculate the equilibrium constant for the reaction.

What is the equilibrium concentration of each of the substances in the equilibrium when the initial concentration of \(ICl\) was \(0.78 \ M\)?
\(2ICl (g) ⇋ I_2 (g) + Cl_2 (g); \ K_c = 0.14\)

Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:
\(CH_3COOH (l) + C_2H_5OH (l) ⇋ CH_3COOC_2H_5 (l) + H_2O (l) \)

1. Write the concentration ratio (reaction quotient), Q_c , for this reaction (note: water is not in excess and is not a solvent in this reaction)
2. At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 mol of ethanol, there is 0.171 mol of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant. 
3. Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K, 0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached?

A sample of pure PCl₅ was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of PCl₅ was found to be \(0.5×10^{–1}\ mol L^{–1}\). If value of K_c is \(8.3×10^{–3}\), what are the concentrations of PCl₃ and Cl₂ at equilibrium?
\(PCl_5 (g) ⇋ PCl_3 (g) + Cl_2(g)\)

Equilibrium constant, K_c for the reaction
\(N_2 (g) + 3H_2 (g) ⇋ 2NH_3 (g)\)
At 500 K is 0.061 At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol L^–1 N₂, 2.0 mol L^–1 H₂ and 0.5 mol L^–1 NH₃. Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?

Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:
\(2BrCl (g) ⇋ Br_2 (g) + Cl_2 (g)\)
for which K_c = 32 at 500 K. If initially pure BrCl is present at a concentration of 3.3 × 10^–3 mol L^–1, what is its molar concentration in the mixture at equilibrium?

At 1127 K and 1 atm pressure, a gaseous mixture of CO and CO₂ in equilibrium with soild carbon has 90.55% CO by mass
\(C(s) + CO_2(g) ⇋ 2CO(g)\)
Calculate K_c for this reaction at the above temperature.

Calculate:

1. ∆G^Θ and 
2. the equilibrium constant for the formation of NO₂ from NO and O₂ at 298 K

\(NO (g) + \frac 12O_2 (g) ⇋ NO_2 (g)\)
where,
 ∆_fG^Θ (NO₂) = 52.0 kJ/mol
∆_fG^Θ (NO) = 87.0 kJ/mol
∆_fG^Θ (O₂) = 0 kJ/mol.

Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?

1. \(PCl_5 (g) ⇋ PCl_3 (g) + Cl_2 (g)\)
2. \(CaO (s) + CO_2 (g) ⇋ CaCO_3 (s)\)
3. \(3Fe (s) + 4H_2O (g) ⇋ Fe_3O_4 (s) + 4H_2 (g)\)

What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species: HNO₂, CN^– , HClO₄,F^–,OH^–,CO and S₂^–

Which of the following are Lewis acids? H₂O, BF₃, H⁺, and NH₄⁺.