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ICSE Class 10 Chemistry Question 51 of 72

Mole Concept & Stoichiometry Miscellaneous Exercises — Question 51

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51
Question

Question 47(d)

Commercial sodium hydroxide weighing 30g has some sodium chloride in it. The Mixture on dissolving in water and subsequent treatment with excess silver nitrate solution formed a precipitate weighing 14.3 g. What is the percentage of sodium chloride in the commercial sample of sodium hydroxide? The equation for the reaction is

NaCl + AgNO3 ⟶ AgCl + NaNO3

(Relative molecular mass of NaCl = 58; AgCl = 143)

Answer

NaCl58g+AgNO3⟶AgCl143 g+NaNO3\underset{58 \text{g}}{\text{NaCl}} + \text{AgNO}_3 \longrightarrow \underset{143 \text{ g}}{\text{AgCl}} + \text{NaNO}_3

(i) 143 g AgCl is formed by 58 g NaCl

∴ 14.3 g of AgCl will be formed by 58143\dfrac{58}{143} x 14.3 = 5.8 g

Percentage of NaCl = 5.830\dfrac{5.8}{30} x 100 = 19.33%

Hence, percentage of NaOH is 19.33%