Question

how many formula units (f.un.) are in 12.5 g nh4cl? (1 mol nh4cl = 53.5 g) (1 mol nh4cl = 6.02 x 10^{23} formula units) ? x 10^{?} f.un. nh4cl enter the coefficient in the green box and the exponent in the yellow box. coefficient (green) exponent (yellow)

Explanation:

Step1: Calculate the number of moles of \(NH_4Cl\)

Use the formula \(n=\frac{m}{M}\), where \(m = 12.5\space g\) (mass of \(NH_4Cl\)) and \(M=53.5\space g/mol\) (molar mass of \(NH_4Cl\)).
\(n=\frac{12.5\space g}{53.5\space g/mol}\approx0.2336\space mol\)

Step2: Calculate the number of formula units

Use the Avogadro's number \(N = n\times N_A\), where \(N_A = 6.02\times 10^{23}\space formula\space units/mol\) and \(n = 0.2336\space mol\)
\(N=0.2336\space mol\times6.02\times 10^{23}\space formula\space units/mol\)
\(N=(0.2336\times6.02)\times 10^{23}\)
\(0.2336\times6.02 = 1.406\)
\(N = 1.406\times 10^{23}\space formula\space units\)

Answer:

Coefficient (green): \(1.4\)
Exponent (yellow): \(23\)