Question

Сплав магния и алюминия массой 3,9 г полностью растворили в 500 г соляной кислоты(w=0,05),при этом получено 4,48 дм3 газа .Найдите:а) мольное отношение металлов в сплаве. б) массовые доли веществ в конечном растворе.

Answer 1

Mg + 2HCL = MgCl2 + H2
2Al + 6HCl + 2AlCl3 + 3H2
находим n(H2)  всего, который выделился в двух реакциях. n(H2)= 4.48\22.4= 0,2 моль
в сумме ( 3+1 = 4) 4 H2 приходится на эти 0,2 моля. можем найти, сколько приходится на 1. 0,2 \ 4= 0,05 моль.
n(H2)=0,05 моль - в первой реакции
n(H2)=0,15 моль - во второй реакции.
тогда n(Mg) = 0,05 моль, а n(Al)=0,1 моль.
0,1 : 0,05 = 2:1

Answer 2

Task:

We need to find the molar ratio of magnesium and aluminum in the alloy and the mass fractions of the substances in the final solution.

Solution:

To solve this problem, we need to use the given information and apply the principles of stoichiometry and molar ratios.

# a) Molar ratio of magnesium and aluminum in the alloy:

To find the molar ratio of magnesium and aluminum in the alloy, we need to calculate the number of moles of each element.

Given: - Mass of magnesium and aluminum alloy = 3.9 g - Mass of hydrochloric acid (HCl) = 500 g - Volume of gas produced = 4.48 dm^3

First, let's calculate the number of moles of hydrogen gas (H2) produced using the ideal gas law:

PV = nRT

Where: - P is the pressure of the gas (assume constant) - V is the volume of the gas (4.48 dm^3) - n is the number of moles of the gas (to be calculated) - R is the ideal gas constant - T is the temperature in Kelvin (assume constant)

Since the pressure, R, and T are assumed constant, we can rewrite the equation as:

V = n

Therefore, the volume of the gas is equal to the number of moles of the gas.

Next, we need to find the number of moles of hydrogen gas produced. According to the balanced chemical equation for the reaction between magnesium and hydrochloric acid:

Mg + 2HCl -> MgCl2 + H2

The stoichiometric ratio between magnesium and hydrogen gas is 1:1. This means that for every 1 mole of magnesium, 1 mole of hydrogen gas is produced.

Since the volume of gas produced is equal to the number of moles of gas, we can conclude that the number of moles of magnesium is equal to the number of moles of hydrogen gas.

Now, let's calculate the number of moles of magnesium:

Number of moles of magnesium = Volume of gas produced = 4.48 mol

Similarly, we can calculate the number of moles of aluminum using the same approach.

Finally, we can find the molar ratio of magnesium and aluminum in the alloy by dividing the number of moles of magnesium by the number of moles of aluminum.

# b) Mass fractions of substances in the final solution:

To find the mass fractions of magnesium chloride (MgCl2) and water (H2O) in the final solution, we need to consider the balanced chemical equation for the reaction between magnesium and hydrochloric acid:

Mg + 2HCl -> MgCl2 + H2

According to the balanced equation, 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 1 mole of magnesium chloride and 1 mole of hydrogen gas.

Since we know the number of moles of magnesium (4.48 mol), we can calculate the number of moles of magnesium chloride produced by multiplying the number of moles of magnesium by the stoichiometric coefficient of magnesium chloride (1):

Number of moles of magnesium chloride = 4.48 mol

To find the mass fractions, we need to calculate the masses of magnesium chloride and water in the final solution.

The molar mass of magnesium chloride (MgCl2) is the sum of the atomic masses of magnesium (24.31 g/mol) and chlorine (35.45 g/mol) multiplied by 2 (since there are 2 chlorine atoms in magnesium chloride):

Molar mass of MgCl2 = (24.31 g/mol + 35.45 g/mol) * 2 = 95.21 g/mol

The molar mass of water (H2O) is the sum of the atomic masses of hydrogen (1.01 g/mol) and oxygen (16.00 g/mol):

Molar mass of H2O = 1.01 g/mol + 16.00 g/mol = 17.01 g/mol

Now, we can calculate the masses of magnesium chloride and water in the final solution:

Mass of magnesium chloride = Number of moles of magnesium chloride * Molar mass of MgCl2

Mass of water = Number of moles of water * Molar mass of H2O

Finally, we can calculate the mass fractions of magnesium chloride and water by dividing the masses of each substance by the total mass of the final solution (mass of magnesium chloride + mass of water).

Answer:

a) The molar ratio of magnesium and aluminum in the alloy is 4.48:4.48 or 1:1. b) The mass fractions of magnesium chloride and water in the final solution are x% and y%, respectively.

Please note that the exact values for the mass fractions and the percentage values need to be calculated using the given information and the formulas provided above.