Question

Помогитеее... При сгорании углеводорода массой 11,4 г выделилось 35,2 г углекислого газа и 16,2 г паров воды. Плотность этого вещества по водороду равна 56. Определите молекулярную формулу вещества. Прошу помощи!!!

Answer 1

M(CxHy) = DH2*MH2 = 56*2 =112 г/моль
n(C) = n(CO2) = m/M = 35,2/44 = 0,8 моль
n(H) = 2n(H2O) = m/M *2 = 16,2/18*2 = 1,8 моль
m(C) = A*n = 0,8*12 = 9,6 г
m(H) = 1,8 г
11,4-9,6-1,8 = 0
n(C):n(H) = 0,8:1,8 = 1:2
CH2
M(CH2) = 14 г/моль
112/14 = 8
C8H16

Answer 2

Calculation of the Molecular Formula of the Substance

To determine the molecular formula of the substance, we need to analyze the given information about the mass of the hydrocarbon, the amount of carbon dioxide and water produced, and the density of the substance.

Given: - Mass of hydrocarbon = 11.4 g - Mass of carbon dioxide produced = 35.2 g - Mass of water vapor produced = 16.2 g - Density of the substance relative to hydrogen = 56

To calculate the molecular formula, we need to find the number of carbon and hydrogen atoms in the hydrocarbon.

1. Calculate the number of moles of carbon dioxide produced: - Moles of carbon dioxide = mass of carbon dioxide / molar mass of carbon dioxide - The molar mass of carbon dioxide (CO2) is 44.01 g/mol. - Moles of carbon dioxide = 35.2 g / 44.01 g/mol

2. Calculate the number of moles of water vapor produced: - Moles of water vapor = mass of water vapor / molar mass of water - The molar mass of water (H2O) is 18.02 g/mol. - Moles of water vapor = 16.2 g / 18.02 g/mol

3. Calculate the number of moles of carbon and hydrogen in the hydrocarbon: - Moles of carbon = moles of carbon dioxide - Moles of hydrogen = 2 * moles of water vapor (since each water molecule contains 2 hydrogen atoms)

4. Calculate the molar mass of the hydrocarbon: - Molar mass of carbon = 12.01 g/mol - Molar mass of hydrogen = 1.01 g/mol - Molar mass of the hydrocarbon = (moles of carbon * molar mass of carbon) + (moles of hydrogen * molar mass of hydrogen)

5. Calculate the empirical formula of the hydrocarbon: - Divide the molar mass of the hydrocarbon by the empirical formula mass to find the empirical formula ratio. - The empirical formula mass is the sum of the molar masses of the atoms in the empirical formula. - The empirical formula ratio will give us the simplest whole number ratio of carbon and hydrogen atoms in the hydrocarbon.

6. Calculate the molecular formula of the hydrocarbon: - The molecular formula is a multiple of the empirical formula. - Multiply the empirical formula by a whole number to obtain the molecular formula.

Let's perform the calculations step by step.

Step 1: Calculate the number of moles of carbon dioxide produced:

Moles of carbon dioxide = 35.2 g / 44.01 g/mol = 0.799 mol

Step 2: Calculate the number of moles of water vapor produced:

Moles of water vapor = 16.2 g / 18.02 g/mol = 0.899 mol

Step 3: Calculate the number of moles of carbon and hydrogen in the hydrocarbon:

Moles of carbon = 0.799 mol Moles of hydrogen = 2 * 0.899 mol = 1.798 mol

Step 4: Calculate the molar mass of the hydrocarbon:

Molar mass of carbon = 12.01 g/mol Molar mass of hydrogen = 1.01 g/mol Molar mass of the hydrocarbon = (0.799 mol * 12.01 g/mol) + (1.798 mol * 1.01 g/mol) = 15.19 g/mol

Step 5: Calculate the empirical formula of the hydrocarbon:

The empirical formula mass is the sum of the molar masses of the atoms in the empirical formula. Empirical formula mass = (molar mass of carbon * number of carbon atoms) + (molar mass of hydrogen * number of hydrogen atoms)

Let's assume the empirical formula has x carbon atoms and y hydrogen atoms.

Empirical formula mass = (12.01 g/mol * x) + (1.01 g/mol * y)

Since the density of the substance relative to hydrogen is given as 56, we can write the following equation:

56 = (12.01 g/mol * x) / (1.01 g/mol * y)

Simplifying the equation, we get:

56 = 11.9x / y

To find the simplest whole number ratio of carbon and hydrogen atoms, we can assume x = 1 and solve for y:

56 = 11.9 / y y = 11.9 / 56 y ≈ 0.212

Since y is not a whole number, we need to multiply both x and y by a common factor to obtain whole numbers. Let's multiply by 10 to get:

x = 10 y = 2

Therefore, the empirical formula of the hydrocarbon is CH2.

Step 6: Calculate the molecular formula of the hydrocarbon:

To find the molecular formula, we need to determine the multiple of the empirical formula.

To calculate the multiple, we divide the molar mass of the hydrocarbon by the molar mass of the empirical formula.

Molar mass of the hydrocarbon = 15.19 g/mol Molar mass of the empirical formula (CH2) = (12.01 g/mol * 1) + (1.01 g/mol * 2) = 14.03 g/mol

Multiple = Molar mass of the hydrocarbon / Molar mass of the empirical formula Multiple = 15.19 g/mol / 14.03 g/mol ≈ 1.08

Since the multiple is approximately 1.08, we can round it to the nearest whole number, which is 1.

Therefore, the molecular formula of the hydrocarbon is also CH2.

In conclusion, the molecular formula of the substance is CH2.

Please let me know if you need any further assistance!