## Chemistry: Molecular Approach (4th Edition)

Published by Pearson

# Chapter 3 - Exercises - Page 132: 72

#### Answer

a. $63.65\%$ b. $46.68\%$ c. $30.45\%$ d. $22.23\%$

#### Work Step by Step

a. 1. Calculate the molar mass of: $N_2O$ Molar Mass ($N_2O$): 14.01* 2 + 16.00* 1 = 44.02g/mol 2. Calculate the total mass of $N$ in one mole of this compound: Total Mass ($N$): $2 \times 14.01g = 28.02g$ 3. Find the mass percent composition: $\frac{Total-mass (N)}{Molar-Mass} \times 100\% = \frac{ 28.02}{ 44.02} \times 100\% = 63.65\%$ b. 1. Calculate the molar mass of: $NO$ Molar Mass ($NO$): 14.01* 1 + 16.00* 1 = 30.01g/mol 2. Calculate the total mass of $N$ in one mole of this compound: Total Mass ($N$): $1 \times 14.01g = 14.01g$ 3. Find the mass percent composition: $\frac{Total-mass (N)}{Molar-Mass} \times 100\% = \frac{ 14.01}{ 30.01} \times 100\% = 46.68\%$ c. 1. Calculate the molar mass of: $NO_2$ Molar Mass ($NO_2$): 14.01* 1 + 16.00* 2 = 46.01g/mol 2. Calculate the total mass of $N$ in one mole of this compound: Total Mass ($N$): $1 \times 14.01g = 14.01g$ 3. Find the mass percent composition: $\frac{Total-mass (N)}{Molar-Mass} \times 100\% = \frac{ 14.01}{ 46.01} \times 100\% = 30.45\%$ d. 1. Calculate the molar mass of: $HNO_3$ Molar Mass ($HNO_3$): 1.008* 1 + 14.01* 1 + 16.00* 3 = 63.02g/mol 2. Calculate the total mass of $N$ in one mole of this compound: Total Mass ($N$): $1 \times 14.01g = 14.01g$ 3. Find the mass percent composition: $\frac{Total-mass (N)}{Molar-Mass} \times 100\% = \frac{ 14.01}{ 63.02} \times 100\% = 22.23\%$

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