Double Displacement Reactions - UNSOLVED PRACTICE SET

Q7. Define double displacement reaction. Write the general equation for a double displacement reaction between two compounds AB and CD.

Q8. Write balanced chemical equations for the following double displacement reactions:

(a) Silver nitrate solution reacts with sodium chloride solution.

(b) Barium chloride solution reacts with sodium sulphate solution.

Q9. Your mother uses alum (potassium aluminium sulphate) to purify muddy water. The dirt particles settle down as a precipitate. Explain the double displacement reaction involved in this process.

Q10. Differentiate between a displacement reaction and a double displacement reaction with one example of each.

Q11. What is a precipitation reaction? Is it always a double displacement reaction? Give an example to support your answer.

Q12. When lead nitrate solution is mixed with potassium iodide solution, a bright yellow precipitate is formed. Write the balanced chemical equation and identify the precipitate.

Q13. Define double displacement reaction and explain its types with examples. Describe: (i) precipitation reactions, (ii) neutralization reactions, and (iii) reactions with evolution of a gas. Write balanced chemical equations for each type and explain the observable changes.

Q14. A student performs the following experiments:

Experiment 1: Mixing sodium carbonate solution with calcium chloride solution

Experiment 2: Mixing sodium hydroxide solution with hydrochloric acid

Experiment 3: Mixing ammonium chloride solution with sodium hydroxide solution

Experiment 4: Mixing potassium sulphate solution with sodium nitrate solution

(a) Identify which experiments show double displacement reactions.

(b) Write balanced chemical equations for the double displacement reactions.

(c) For each reaction, identify the type of double displacement (precipitation, neutralization, or gas evolution).

(d) Explain why Experiment 4 does not show any visible reaction.

(e) What would you observe in each experiment that shows a reaction?

Q15. "Double displacement reactions are among the most common reactions in aqueous solutions and have numerous applications in daily life and industry." Discuss this statement by explaining: (i) how precipitation reactions are used in water treatment, (ii) how neutralization reactions are used in antacids and agriculture, (iii) how double displacement reactions are used in qualitative analysis to identify ions, and (iv) their role in the manufacture of important chemicals.

Q16. In a chemistry laboratory, a student performs double displacement reactions to identify unknown solutions:

Table

Test Observation

Solution X + AgNO₃ White precipitate

Solution Y + BaCl₂ White precipitate

Solution Z + NaOH White precipitate, soluble in excess NaOH

(a) Identify the possible anion in Solution X.

(b) Identify the possible anion in Solution Y.

(c) Identify the possible cation in Solution Z.

(d) If Solution X is sodium chloride and 5.85 g of it reacts with excess silver nitrate, calculate the mass of silver chloride precipitated. (Molar masses: NaCl = 58.5 g/mol, AgCl = 143.5 g/mol)

(e) Write balanced chemical equations for all three tests.

Q17. A water treatment plant uses double displacement reactions to remove hardness from water:

Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃ + 2H₂O

(a) Is this a double displacement reaction? Give a reason.

(b) If a water sample contains 162 mg/L of calcium bicarbonate, calculate the mass of calcium carbonate precipitated when 1000 L of this water is treated. (Molar masses: Ca(HCO₃)₂ = 162 g/mol, CaCO₃ = 100 g/mol)

(c) The plant also uses sodium carbonate to remove permanent hardness:

CaCl₂ + Na₂CO₃ → CaCO₃ + 2NaCl

If 111 kg of calcium chloride is present in the water, calculate the mass of sodium carbonate needed for complete reaction. (Molar masses: CaCl₂ = 111 g/mol, Na₂CO₃ = 106 g/mol)

(d) Why is removing water hardness important for Indian households and industries?

(e) Calculate the mass of CaCO₃ precipitated from 111 kg of CaCl₂.

Q18. In a school science project, students investigate antacids used to treat acidity. They test various antacid tablets containing sodium bicarbonate (NaHCO₃) and magnesium hydroxide (Mg(OH)₂).

(a) Write balanced equations for the reaction of each antacid with stomach acid (HCl).

(b) If a tablet contains 840 mg of NaHCO₃, calculate the mass of HCl it can neutralize. (Molar masses: NaHCO₃ = 84 g/mol, HCl = 36.5 g/mol)

(c) If another tablet contains 580 mg of Mg(OH)₂, calculate the mass of HCl it can neutralize. (Molar mass: Mg(OH)₂ = 58 g/mol)

(d) Which antacid is more effective per gram? Show your calculation.

(e) Why do doctors sometimes recommend magnesium hydroxide over sodium bicarbonate for long-term use?