Question

СРОЧНО ПОМОГИТЕ!!!!!!!!!В раствор серной кислоты опустили цинковую пластинку. После завершения реакции по серной кислоте образовался раствор с массовой долей сульфата цинка 10%. Вычислите массовую долю серной кислоты в исходном растворе. Ответ дайте в процентах с точностью до десятых без указания знака процента.

Answer 1

Ответ:

Уравнение реакции:

Zn (M = 65 г/моль) + H2SO4 (M = 98 г/моль) = ZnSO4 (M = 161 г/моль) + H2 (M = 2 г/моль);

Пусть масса полученного р-ра = 100 г., тогда масса ZnSO4 = 10 г., что составляет 10/161 = 0.0621 моль;

помимо ZnSO4, образовался H2 массой 2×0.0621 = 0.1242 г;

в реакцию вступили цинк массой 65×0.0621 = 4.0365 г. и H2SO4 массой 98×0.0621 = 6.0858 г.;

масса полученного р-ра = (масса исх. р-ра H2SO4+масса цинка)-масса H2 = 100 г., тогда масса исх. р-ра = (100+0.1242)-4.0365 = 96.0877 г.;

w H2SO4 в исх. р-ре = 6.0858/96.0877 ≈ 0.06334 или 6.334%;

Ответ: 6.3.

Answer 2

Calculation of the Mass Fraction of Sulfuric Acid in the Initial Solution

To calculate the mass fraction of sulfuric acid in the initial solution, we need to use the information provided. According to the question, a zinc plate was immersed in a solution of sulfuric acid, and after the reaction, a solution with a mass fraction of zinc sulfate of 10% was obtained.

To find the mass fraction of sulfuric acid, we can assume that the mass of the zinc plate remains constant throughout the reaction. This assumption allows us to calculate the mass of zinc sulfate formed and then determine the mass of sulfuric acid in the initial solution.

Let's denote the mass of the initial solution as M grams. Since the mass fraction of zinc sulfate is given as 10%, we can calculate the mass of zinc sulfate formed as 0.1 times the mass of the initial solution:

Mass of zinc sulfate = 0.1 × M grams Since zinc sulfate is formed by the reaction of zinc with sulfuric acid, the molar ratio between zinc and zinc sulfate is 1:1. Therefore, the molar mass of zinc sulfate is equal to the molar mass of zinc (65.38 g/mol).

To calculate the mass of sulfuric acid in the initial solution, we need to subtract the mass of zinc sulfate formed from the mass of the initial solution:

Mass of sulfuric acid = Mass of initial solution - Mass of zinc sulfate

Since the mass of the initial solution is equal to the sum of the mass of zinc sulfate and the mass of sulfuric acid, we can rewrite the equation as:

Mass of sulfuric acid = Mass of initial solution - 0.1 × M grams

To find the mass fraction of sulfuric acid, we divide the mass of sulfuric acid by the mass of the initial solution and multiply by 100:

Mass fraction of sulfuric acid = (Mass of sulfuric acid / Mass of initial solution) × 100

Let's calculate the mass fraction of sulfuric acid using the given information:

Mass fraction of sulfuric acid = (Mass of sulfuric acid / Mass of initial solution) × 100

Substituting the equation for the mass of sulfuric acid, we get:

Mass fraction of sulfuric acid = [(Mass of initial solution - 0.1 × M grams) / Mass of initial solution] × 100

Simplifying the equation, we have:

Mass fraction of sulfuric acid = (1 - 0.1) × 100

Therefore, the mass fraction of sulfuric acid in the initial solution is 90% with an accuracy of one decimal place.

Please note that the calculation assumes that the reaction goes to completion and that there are no other substances present in the solution that could affect the calculation.