Question

Какую молекулярную формулу имеет органическое вещество, если при сгорании 12 г образовались оксид углерода (IV) массой 35,2 г и вода массой 21,6 г. Плотность этого вещества равна 1, 35 г/л.

Answer 1

Дано:
m(в-ва) = 12 г
m(CO2)=35,2 r
m(H2O)=21.6 r
ρ=1,35 г/л
Найти:
Мол. формулу-?

n=m/M
M(CO2)=44 г/моль
n(CO2) = 35,2 г/44 г/моль = 0,8 моль
n(C)=n(CO2)
n(C)=0,8 моль
m(C)= n/M = 0,8 моль*12 г/моль = 9,6 г
n(H2O) = 21.6 г/18 г/моль = 1,2 моль
n(H)=2n(H2O)
n(H) = 2*1,2 моль = 2,4 моль
m(H) = 2.4 моль*1 г/моль = 2,4 г
m(O)= 12 г-9,6 г-2,4 г = 0 г
С:H = 0,8:2,4 = 1:3
Простейшая формула: СН3
М(СН3) = 15 г/моль
М(в-ва) =ρ*Vm = 1,35 г/л*22,4 л/моль = 30 г/моль
30 г/моль/15 г/моль = 2
Следовательно, молекулярная формула С2Н6 является истиной.
Ответ: С2Н6 - этан

Answer 2

Molecular Formula of the Organic Substance

To determine the molecular formula of the organic substance, we can use the information provided about the combustion of the substance and the resulting products.

According to the information given, when 12 g of the organic substance is burned, it produces carbon dioxide (CO2) with a mass of 35.2 g and water (H2O) with a mass of 21.6 g.

To find the molecular formula, we need to calculate the number of moles of carbon dioxide and water produced.

The molar mass of carbon dioxide (CO2) is 44 g/mol, and the molar mass of water (H2O) is 18 g/mol.

Let's calculate the number of moles of carbon dioxide and water:

- Moles of carbon dioxide = mass of carbon dioxide / molar mass of carbon dioxide - Moles of carbon dioxide = 35.2 g / 44 g/mol = 0.8 mol

- Moles of water = mass of water / molar mass of water - Moles of water = 21.6 g / 18 g/mol = 1.2 mol

Now, we need to find the ratio of carbon to hydrogen in the organic substance.

From the balanced equation for the combustion of organic compounds, we know that for every 1 mole of carbon dioxide produced, there are 1 mole of carbon atoms. Similarly, for every 1 mole of water produced, there are 2 moles of hydrogen atoms.

Therefore, the ratio of carbon to hydrogen in the organic substance is 1:2.

The empirical formula of the organic substance is CH2.

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

The molecular mass of CH2 is 14 g/mol (12 g/mol for carbon + 2 g/mol for hydrogen).

To calculate the molecular formula, we divide the molar mass of the empirical formula (14 g/mol) into the molar mass of the organic substance.

The molar mass of the organic substance can be calculated using the density provided.

The density of the substance is given as 1.35 g/L.

We can use the density to calculate the molar mass of the substance:

- Molar mass of the substance = density * molar volume - Molar volume = 1 L/mol (from the ideal gas law) - Molar mass of the substance = 1.35 g/L * 1 L/mol = 1.35 g/mol

Now, we can calculate the molecular formula:

- Molecular formula = (molar mass of the substance) / (molar mass of the empirical formula) - Molecular formula = 1.35 g/mol / 14 g/mol = 0.0964

Since the result is less than 1, we need to multiply the empirical formula by a whole number to obtain the molecular formula.

To find this whole number, we divide 1 by the result obtained:

- Whole number = 1 / 0.0964 = 10.36

Rounding to the nearest whole number, we get 10.

Therefore, the molecular formula of the organic substance is C10H20.

Please note that the sources provided did not directly answer the question. The answer was derived using the principles of stoichiometry and molar mass calculations.