Question

how many formula units (f.un.) are in 35.0 g kno₃? (1 mol kno₃ = 101.11 g) (1 mol kno₃ = 6.02 × 10²³ formula units) ? × 10^{?} f.un. kno₃ enter the coefficient in the green box and the exponent in the yellow box.

Explanation:

Step1: Calculate moles of KNO₃

Use the formula \(n=\frac{m}{M}\), where \(m = 35.0\space g\) (mass of \(KNO_3\)) and \(M=101.11\space g/mol\) (molar mass of \(KNO_3\)).
\(n=\frac{35.0\space g}{101.11\space g/mol}\approx0.346\space mol\)

Step2: Calculate formula units

Use Avogadro's number (\(N_A = 6.02\times 10^{23}\space f.un./mol\)).
\(N=n\times N_A\)
\(N = 0.346\space mol\times6.02\times 10^{23}\space f.un./mol\)
\(N=(0.346\times6.02)\times10^{23}\)
\(0.346\times6.02 = 2.08\)
\(N = 2.08\times 10^{23}\space f.un.\)

Answer:

Coefficient (green): \(2.08\)
Exponent (yellow): \(23\)