Based on Table G, what is the approximate mass of \( \mathrm{NH}_{3} \) that must be dissolved in 200 grams of water to produce a saturated solution at \( 20 .{ }^{\circ} \mathrm{C} \) ?
1. \( 28 \mathrm{~g} \)
2. \( 56 \mathrm{~g} \)
3. \( \quad 100 \mathrm{~g} \)
4. \( \quad 112 \mathrm{~g} \)
Answer
\( m_2 = \frac{m_1 \times s}{1 + s} = \frac{200 \mathrm{~g} \times \frac{112 \mathrm{~g~NH_3}}{100 \mathrm{~g~H_2O}}}{1 + \frac{112 \mathrm{~g~NH_3}}{100 \mathrm{~g~H_2O}}} \)
Step 1 ：\( m_1 = 200 \mathrm{~g} \)
Step 2 ：\( s = \frac{112 \mathrm{~g~NH_3}}{100 \mathrm{~g~H_2O}} \)
Step 3 ：\( m_2 = \frac{m_1 \times s}{1 + s} = \frac{200 \mathrm{~g} \times \frac{112 \mathrm{~g~NH_3}}{100 \mathrm{~g~H_2O}}}{1 + \frac{112 \mathrm{~g~NH_3}}{100 \mathrm{~g~H_2O}}} \)
