Question

Calculate the mass of potassium cyanide ion that must be added to 100 mL of solution to dissolve 2.0 × 10⁻² mol of silver cyanide, AgCN.

a) 0.03 g

b) 0.06 g

c) 0.15 g

d) 0.30 g

Answer 1

To dissolve 2.0 × 10⁻² moles of AgCN, an equal amount of KCN is required. The calculated mass of KCN needed is 1.3024 g, which does not match any of the given options, indicating a possible typo in the question or answers.

Step-by-step explanation:

To calculate the mass of potassium cyanide (KCN) that must be added to dissolve 2.0 × 10⁻² moles of silver cyanide (AgCN), we need to consider the stoichiometry of the reaction between AgCN and KCN.

AgCN(s) + KCN(aq) → K[Ag(CN)₂](aq)

From the reaction, it is clear that each mole of AgCN reacts with one mole of KCN. Therefore, 2.0 × 10⁻² moles of AgCN will require the same amount of KCN to dissolve.

The molar mass of KCN is approximately 65.12 g/mol. Thus, the mass of KCN needed can be calculated as follows:

Mass of KCN = Moles of KCN × Molar mass of KCN
Mass of KCN = (2.0 × 10⁻² mol) × (65.12 g/mol)
Mass of KCN = 1.3024 g

Since none of the answer choices match the calculated mass (1.3024 g), we need to consider the volume of the solution. However, the volume does not affect the amount of KCN needed to react with a given amount of AgCN. Therefore, the correct mass is still 1.3024 g, which is not presented in the given options, suggesting that there might be a typo in the question or the answer choices provided.