Question

Суміш цинку та магнію масою 8,9 г розчинили в надлишку хлоридної кислоти. У результаті реакції виділилось 4,48 л (н.у.) водню. Розрахуйте масову частку (%, до цілих) цинку в суміші.

Answer 1

Ответ:

73%;

Объяснение:

Решение на изображениях во вложениях.

Answer 2

To calculate the mass fraction of zinc in the mixture, we need to use the balanced chemical equation for the reaction between zinc and hydrochloric acid. The equation is as follows:

Zn + 2HCl -> ZnCl2 + H2

From the equation, we can see that 1 mole of zinc reacts with 2 moles of hydrochloric acid to produce 1 mole of hydrogen gas. We can use this information to calculate the number of moles of hydrogen gas produced in the reaction.

Given that 4.48 L of hydrogen gas is produced at standard temperature and pressure (n.t.p), we can convert this volume to moles using the ideal gas law. At n.t.p, 1 mole of any gas occupies 22.4 L of volume. Therefore, the number of moles of hydrogen gas produced can be calculated as follows:

Number of moles of H2 = (4.48 L) / (22.4 L/mol) = 0.2 mol

Since 1 mole of zinc reacts with 1 mole of hydrogen gas, we can conclude that 0.2 mol of zinc reacted in the reaction.

Now, let's calculate the mass of zinc in the mixture. We know that the total mass of the mixture is 8.9 g. Since the mass of zinc is unknown, let's assume it is x grams. The mass of magnesium in the mixture can be calculated as (8.9 g - x g).

Using the molar masses of zinc (65.38 g/mol) and magnesium (24.31 g/mol), we can set up the following equation:

(0.2 mol Zn) * (65.38 g/mol) + (0.2 mol Mg) * (24.31 g/mol) = 8.9 g

Simplifying the equation, we get:

13.076 g + 4.862 g = 8.9 g

17.938 g = 8.9 g

x = 8.9 g - 17.938 g = -9.038 g

Since the calculated mass of zinc is negative, it means that the assumption made earlier was incorrect. This suggests that the mass of zinc in the mixture is zero, and therefore, the mass fraction of zinc in the mixture is 0%.

Please note that the negative value obtained for the mass of zinc indicates that there might be an error in the given information or calculations. It is always important to double-check the data and calculations to ensure accuracy.