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When 50 mL50\text{ mL} of a 16.9% (w/v)16.9\%\text{ (w/v)} solution of AgNO3\text{AgNO}_3 is mixed with 50 mL50\text{ mL} of 5.8% (w/v) NaCl5.8\%\text{ (w/v) NaCl} solution, then the mass of precipitate formed is: (Ag=107.8\text{Ag} = 107.8, N=14\text{N} = 14, O=16\text{O} = 16, Na=23\text{Na} = 23, Cl=35.5\text{Cl} = 35.5)

A

28 g28\text{ g}

B

3.5 g3.5\text{ g}

C

7 g7\text{ g}

D

14 g14\text{ g}

Step-by-Step Solution

Mass of AgNO3\text{AgNO}_3 in 50 mL50\text{ mL} of 16.9% (w/v)16.9\%\text{ (w/v)} solution = 16.9100×50=8.45 g\frac{16.9}{100} \times 50 = 8.45\text{ g}. Molar mass of AgNO3=107.8+14+(16×3)=169.8 g/mol\text{AgNO}_3 = 107.8 + 14 + (16 \times 3) = 169.8\text{ g/mol}. Moles of AgNO3=8.45169.80.0497 mol\text{AgNO}_3 = \frac{8.45}{169.8} \approx 0.0497\text{ mol}.

Mass of NaCl\text{NaCl} in 50 mL50\text{ mL} of 5.8% (w/v)5.8\%\text{ (w/v)} solution = 5.8100×50=2.9 g\frac{5.8}{100} \times 50 = 2.9\text{ g}. Molar mass of NaCl=23+35.5=58.5 g/mol\text{NaCl} = 23 + 35.5 = 58.5\text{ g/mol}. Moles of NaCl=2.958.50.0495 mol\text{NaCl} = \frac{2.9}{58.5} \approx 0.0495\text{ mol}.

The balanced chemical equation is: AgNO3+NaClAgCl+NaNO3\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl}\downarrow + \text{NaNO}_3

From the stoichiometry, 1 mole1\text{ mole} of AgNO3\text{AgNO}_3 reacts with 1 mole1\text{ mole} of NaCl\text{NaCl}. Here, the moles of NaCl\text{NaCl} (0.0495 mol0.0495\text{ mol}) are slightly less than the moles of AgNO3\text{AgNO}_3 (0.0497 mol0.0497\text{ mol}), making NaCl\text{NaCl} the limiting reagent.

Moles of AgCl\text{AgCl} precipitate formed = Moles of NaCl\text{NaCl} reacted = 0.0495 mol0.0495\text{ mol}. Molar mass of AgCl=107.8+35.5=143.3 g/mol\text{AgCl} = 107.8 + 35.5 = 143.3\text{ g/mol}. Mass of AgCl\text{AgCl} formed = Moles ×\times Molar mass = 0.0495 mol×143.3 g/mol7.09 g7 g0.0495\text{ mol} \times 143.3\text{ g/mol} \approx 7.09\text{ g} \approx 7\text{ g}.

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