Question

Сплав латунь массой 78г вытесняет из соляной кислоты 13,44л газа( при н.у.) найдите массовую долю меди в сплаве

Answer 1

Латунь — сплав меди с цинком. С соляной кислотой будет взаимодействовать только цинк (он стоит левее водорода в электрохимическом ряду).
Уравнение реакции:
Zn + 2HCl = ZnCl2 + H2
Количество вещества  соляной кислоты = 13,44/22,4 = 0,6 моль.
Количество вещества цинка такое же. а его молярная масса равна 65 гр/моль.
Значит. масса цинка в сплаве равна 65х0,6 = 39 грамм.
Это ровно 50% от массы сплава.
Остальное — медь.
Ответ: массовая доля меди в сплаве равна 50%.

Answer 2

Calculating the Mass Fraction of Copper in the Alloy

To calculate the mass fraction of copper in the alloy, we can use the given information about the displacement of gas from hydrochloric acid by the brass alloy.

The reaction of brass with hydrochloric acid can be represented as: Cu + 4HCl → CuCl2 + 2H2 + 2Cl2

From the reaction, we can see that 1 mole of copper displaces 2 moles of hydrogen gas.

Given: - Mass of brass = 78g - Volume of hydrogen gas displaced = 13.44L (at standard conditions)

First, we need to calculate the moles of hydrogen gas displaced by the brass alloy.

Calculating Moles of Hydrogen Gas Displaced

Using the ideal gas law: PV = nRT Where: - P = pressure (at standard conditions, this is 1 atm) - V = volume of gas (13.44L) - n = moles of gas - R = ideal gas constant - T = temperature (at standard conditions, this is 273.15K)

We can rearrange the equation to solve for n: n = PV / RT

Substituting the given values: n = (1 atm) * (13.44L) / (0.0821 L*atm/mol*K * 273.15K)

Calculating n gives us the moles of hydrogen gas displaced.

Calculating the Mass Fraction of Copper

Now that we have the moles of hydrogen gas displaced, we can use the stoichiometry of the reaction to find the moles of copper present in the alloy.

Given that 1 mole of copper displaces 2 moles of hydrogen gas, we can calculate the moles of copper present in the alloy.

Finally, to find the mass fraction of copper in the alloy, we divide the mass of copper by the total mass of the alloy.

Let's calculate these values.