Question

При сгорании органического вещества массой 3 г получили 8,8 г углекислого газа и 5,4 г воды. Относительная плотность этого вещества по водороду равна 15. Установите молекулярную формулу вещества.

Answer 1

Решение на 2х листах см фото

Answer 2

Calculation of Molecular Formula

To determine the molecular formula of the organic substance, we need to analyze the given information.

We are given that the mass of the organic substance is 3 g. When it undergoes combustion, it produces 8.8 g of carbon dioxide (CO2) and 5.4 g of water (H2O).

To find the molecular formula, we need to calculate the number of moles of carbon dioxide and water produced. We can then use the molar ratios to determine the empirical formula, which represents the simplest whole number ratio of atoms in a compound. Finally, we can calculate the molecular formula using the relative molecular mass of the compound.

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

- Moles of CO2 = mass of CO2 / molar mass of CO2 - Moles of H2O = mass of H2O / molar mass of H2O

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

Moles of CO2 = 8.8 g / 44 g/mol = 0.2 mol Moles of H2O = 5.4 g / 18 g/mol = 0.3 mol

Now, let's determine the empirical formula using the molar ratios:

The ratio of carbon dioxide to water is 0.2 mol CO2 : 0.3 mol H2O, which simplifies to 2:3.

Therefore, the empirical formula of the organic substance is C2H3.

To find the molecular formula, we need to know the relative molecular mass of the compound. The relative molecular mass is given as the relative density of the substance with respect to hydrogen, which is 15.

The relative molecular mass can be calculated using the formula:

Relative molecular mass = (Empirical formula mass) * n

Where n is a positive integer.

The empirical formula mass of C2H3 can be calculated as follows:

Empirical formula mass = (2 * atomic mass of carbon) + (3 * atomic mass of hydrogen)

The atomic mass of carbon is approximately 12 g/mol, and the atomic mass of hydrogen is approximately 1 g/mol.

Empirical formula mass = (2 * 12 g/mol) + (3 * 1 g/mol) = 27 g/mol

Now, let's calculate the value of n:

Relative molecular mass = (Empirical formula mass) * n 15 = 27 g/mol * n n = 15 / 27 n ≈ 0.56

Since n should be a positive integer, we need to round it to the nearest whole number. In this case, n is approximately 1.

Therefore, the molecular formula of the organic substance is C2H3.

Note: The given information does not provide enough data to determine the specific compound or its molecular formula with certainty. The calculation assumes that all the carbon in the organic substance is converted to carbon dioxide and all the hydrogen is converted to water during combustion. Additionally, the relative density of the substance with respect to hydrogen is used as an approximation for the relative molecular mass.