Question

a solution is made by dissolving 27.5 g of ammonium cyanide, nh₄cn, in enough water to make exactly 250 ml of solution. calculate the concentration (molarity) of nh₄cn in mol/l (m). m nh₄cn

Explanation:

Step1: Calculate moles of NH₄CN

First, find the molar - mass of NH₄CN. The molar mass of N = 14.01 g/mol, H = 1.01 g/mol, C = 12.01 g/mol.
The molar mass of NH₄CN: \(M=(14.01 + 4\times1.01+12.01 + 14.01)\text{ g/mol}=44.05\text{ g/mol}\)
The number of moles of NH₄CN, \(n=\frac{m}{M}\), where \(m = 27.5\text{ g}\) and \(M = 44.05\text{ g/mol}\)
\(n=\frac{27.5\text{ g}}{44.05\text{ g/mol}}\approx0.624\text{ mol}\)

Step2: Convert volume to liters

The volume of the solution \(V = 250\text{ mL}=0.250\text{ L}\)

Step3: Calculate molarity

The formula for molarity \(M=\frac{n}{V}\)
\(M=\frac{0.624\text{ mol}}{0.250\text{ L}} = 2.496\text{ mol/L}\approx2.50\text{ mol/L}\)

Answer:

2.50 mol/L