A 15.00 gram sample of a solution of sodium chloride (NaCI) in water was heated

Question

A 15.00 gram sample of a solution of sodium chloride (NaCI) in water was heated until all the water had evaporated. The sodium chloride that remained weighed 3.79 grams. Calculate the mass of NaCI and percentage of NaCI in the solution. Show method. Problem solving: % NaCI __________% NaCI A sample of a salt solution is heated until all of the water is driven off leaving the solid salt. These weights were obtained: empty evaporating dish, 71.084 g: evaporating dish plus sample, 75.082 g: evaporating dish plus sample after heating, 73.664 g. Calculate the grams of sample, the grams of salt and % salt in the solution. Show method. Problem solving: g sample: _______g sample g salt: ________g salt % salt: ______% salt

Explanation / Answer

Ans. 2. Mass of NaCl (solute) obtained = 3.79 g

Mass of solution = 15.00 g

% NaCl in solution = (Mass of NaCl / Mass of solution) x 100

                                    = (3.79 g/ 15.00g) x 100

                                    = 25.27%

#3. Given,

I. Weight of empty evaporating disk = 71.084 g

II. Weight of evaporating disk + Sample = 75.082 g

III. Weigh of ‘evaporating disk + Sample’ after heating = 73.664 g

Now,

Part A: Weight of sample (solution) =

(Weight of evaporating disk + Sample) - Weight of empty evaporating disk

= 75.082 g – 71.084 g

= 3.998 g

Part B: Weight of salt =

Wt. of ‘evaporating disk + Sample’ after heating – Wt. of empty evaporating disk

            = 73.664 g – 71.084 g

            = 2.580 g

Part C: % Salt = (Weight of salt / Weight of solution) x 100

                        = (2.580 g / 3.998 g) x 100

                        = 64.53 %

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