Question

При сжигании 2.7 г углеводорода получили 8.8 г углекислого газа и 2.7 г воды. Найти молекулярную формулу этого углеводорода, если относительная плотность вещества по водороду равна 27.

Answer 1

M(CxHy)= 27*2=54г/моль
n(C)=n(CO2)=8,8 г/44г/моль= 0,2 моль; 
n(H)=2n(H2O) = 2*2,7г/18г/моль=0,3 моль; 
n(C):n(H)= 0,2:0,3= 2:3.
Простейшая формула С2Н3; М(С2Н3)= 27, следовательно формула вещества С4Н6

Answer 2

Finding the Molecular Formula of the Hydrocarbon

To find the molecular formula of the hydrocarbon, we need to analyze the given information about the products formed during its combustion.

According to the information provided, when 2.7 g of the hydrocarbon is burned, 8.8 g of carbon dioxide (CO2) and 2.7 g of water (H2O) are produced.

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

Calculating the Moles of Carbon Dioxide and Water

To calculate the moles of a substance, we can use the formula:

moles = mass / molar mass

The molar mass of carbon dioxide (CO2) is calculated by adding the atomic masses of carbon (C) and oxygen (O):

molar mass of CO2 = atomic mass of C + 2 * atomic mass of O

Similarly, the molar mass of water (H2O) is calculated by adding the atomic masses of hydrogen (H) and oxygen (O):

molar mass of H2O = 2 * atomic mass of H + atomic mass of O

Using the atomic masses from the periodic table, we can calculate the moles of carbon dioxide and water produced.

Calculation:

1. Moles of carbon dioxide (CO2): - Molar mass of carbon dioxide (CO2) = atomic mass of C + 2 * atomic mass of O - Molar mass of carbon dioxide (CO2) = 12.01 g/mol + 2 * 16.00 g/mol - Molar mass of carbon dioxide (CO2) = 44.01 g/mol

- Moles of carbon dioxide (CO2) = mass of carbon dioxide (CO2) / molar mass of carbon dioxide (CO2) - Moles of carbon dioxide (CO2) = 8.8 g / 44.01 g/mol - Moles of carbon dioxide (CO2) = 0.1998 mol

2. Moles of water (H2O): - Molar mass of water (H2O) = 2 * atomic mass of H + atomic mass of O - Molar mass of water (H2O) = 2 * 1.01 g/mol + 16.00 g/mol - Molar mass of water (H2O) = 18.02 g/mol

- Moles of water (H2O) = mass of water (H2O) / molar mass of water (H2O) - Moles of water (H2O) = 2.7 g / 18.02 g/mol - Moles of water (H2O) = 0.1498 mol

Determining the Empirical Formula

The empirical formula represents the simplest whole-number ratio of atoms in a compound. To determine the empirical formula, we need to find the ratio of moles of carbon dioxide (CO2) to moles of water (H2O).

From the calculations above, we have: - Moles of carbon dioxide (CO2) = 0.1998 mol - Moles of water (H2O) = 0.1498 mol

To find the ratio, we can divide both values by the smaller value (0.1498 mol in this case):

- Moles of carbon dioxide (CO2) / Moles of water (H2O) = 0.1998 mol / 0.1498 mol ≈ 1.334

Since the ratio is approximately 1.334, we can round it to the nearest whole number to determine the empirical formula.

The empirical formula of the hydrocarbon is therefore C1H1.

Determining the Molecular Formula

To find the molecular formula, we need to know the relative molecular mass of the hydrocarbon. The relative molecular mass is the sum of the atomic masses of all the atoms in the molecular formula.

Given that the relative density of the substance with respect to hydrogen is 27, we can use this information to determine the relative molecular mass.

The relative molecular mass is equal to the molar mass of the substance divided by the molar mass of hydrogen:

Relative molecular mass = molar mass of substance / molar mass of hydrogen

The molar mass of hydrogen is approximately 1.01 g/mol.

Using the relative density of 27, we can calculate the molar mass of the substance:

Molar mass of substance = relative density * molar mass of hydrogen

Molar mass of substance = 27 * 1.01 g/mol

Molar mass of substance = 27.27 g/mol

Now, we can determine the molecular formula by comparing the molar mass of the substance to the empirical formula.

The molar mass of the empirical formula (C1H1) is approximately 12.01 g/mol + 1.01 g/mol = 13.02 g/mol.

To find the molecular formula, we divide the molar mass of the substance by the molar mass of the empirical formula:

Molecular formula = Molar mass of substance / Molar mass of empirical formula

Molecular formula = 27.27 g/mol / 13.02 g/mol

Molecular formula ≈ 2.097

Since the result is approximately 2.097, we can round it to the nearest whole number to determine the molecular formula.

Therefore, the molecular formula of the hydrocarbon is C2H2.

Please note that the molecular formula is an approximation based on the given information and the assumptions made during the calculations.

Answer 3

Finding the Molecular Formula of the Hydrocarbon

To find the molecular formula of the hydrocarbon, we need to analyze the given information about the products of its combustion.

According to the information provided, when 2.7 grams of the hydrocarbon are burned, 8.8 grams of carbon dioxide (CO2) and 2.7 grams of water (H2O) are produced.

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

Calculating the Moles of Carbon Dioxide and Water

To calculate the moles of carbon dioxide and water, we need to use the molar masses of carbon dioxide and water.

The molar mass of carbon dioxide (CO2) is calculated as follows: - The molar mass of carbon (C) is approximately 12.01 grams/mol. - The molar mass of oxygen (O) is approximately 16.00 grams/mol. - Since carbon dioxide contains one carbon atom and two oxygen atoms, the molar mass of carbon dioxide is 12.01 + (2 * 16.00) = 44.01 grams/mol.

The molar mass of water (H2O) is calculated as follows: - The molar mass of hydrogen (H) is approximately 1.01 grams/mol. - The molar mass of oxygen (O) is approximately 16.00 grams/mol. - Since water contains two hydrogen atoms and one oxygen atom, the molar mass of water is (2 * 1.01) + 16.00 = 18.02 grams/mol.

Now, we can calculate the number of moles of carbon dioxide and water produced:

- Moles of carbon dioxide = mass of carbon dioxide / molar mass of carbon dioxide - Moles of carbon dioxide = 8.8 grams / 44.01 grams/mol

- Moles of water = mass of water / molar mass of water - Moles of water = 2.7 grams / 18.02 grams/mol

Determining the Empirical Formula

To determine the empirical formula, we need to find the simplest whole-number ratio between the moles of carbon dioxide and water.

Dividing the moles of carbon dioxide and water by their respective smallest values will give us the simplest ratio.

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

- Moles of carbon dioxide = 8.8 grams / 44.01 grams/mol = 0.1996 mol - Moles of water = 2.7 grams / 18.02 grams/mol = 0.1498 mol

Now, let's divide the moles of carbon dioxide and water by their smallest value (0.1498 mol):

- Moles of carbon dioxide / 0.1498 mol = 0.1996 mol / 0.1498 mol ≈ 1.331 - Moles of water / 0.1498 mol = 0.1498 mol / 0.1498 mol = 1.000

The ratio of moles is approximately 1.331:1.000, which can be simplified to 4:3.

Determining the Molecular Formula

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

The molecular mass of the hydrocarbon can be calculated by adding the molar masses of carbon and hydrogen.

Since the relative density of the substance with respect to hydrogen is given as 27, we can assume that the molar mass of hydrogen is approximately 1 gram/mol.

Let's calculate the molecular mass of the hydrocarbon:

- Molecular mass of hydrogen (H) = 1 gram/mol - Molecular mass of carbon (C) = 12.01 grams/mol

The molecular mass of the hydrocarbon can be represented as 4x(C) + 3x(H), where x is the number of moles.

Since the ratio of moles is 4:3, we can assume x = 3.

- Molecular mass of the hydrocarbon = 4 * 12.01 grams/mol + 3 * 1 gram/mol = 48.04 grams/mol + 3 grams/mol = 51.04 grams/mol

Therefore, the molecular formula of the hydrocarbon is C3H4.

Please note that the given information does not provide enough details to determine the specific name or structure of the hydrocarbon.