Question

Алкан сожгли в избытке кислорода и продукты реакции про пустили через избыток раствора NaOH массой 99,2 г. В результате масса раствора стала равной 100 г, а массовая доля карбоната натрия в растворе составила 1,06 %. Определите формулу алкана.

Answer 1

Вот решение. Удачи!

Answer 2

Determining the Formula of the Alkane

To determine the formula of the alkane, we need to analyze the given information. Let's break it down step by step:

1. The alkane was burned in an excess of oxygen. This means that the alkane was completely oxidized to produce carbon dioxide (CO2) and water (H2O) as the only products.

2. The products of the reaction were passed through an excess of a sodium hydroxide (NaOH) solution. This suggests that the purpose of passing the products through the NaOH solution was to absorb the carbon dioxide produced.

3. The mass of the NaOH solution increased from 99.2 g to 100 g. This indicates that the carbon dioxide was absorbed by the NaOH solution.

4. The mass fraction of sodium carbonate (Na2CO3) in the solution was found to be 1.06%.

Based on this information, we can deduce the following:

- The increase in mass of the NaOH solution (from 99.2 g to 100 g) corresponds to the mass of the absorbed carbon dioxide.

- The mass fraction of sodium carbonate (Na2CO3) in the solution indicates the amount of carbon dioxide that reacted with the NaOH to form sodium carbonate.

To determine the formula of the alkane, we need to calculate the amount of carbon dioxide produced and the amount of sodium carbonate formed.

Let's perform the calculations:

1. Calculate the mass of carbon dioxide produced: - The increase in mass of the NaOH solution is 100 g - 99.2 g = 0.8 g. - This increase in mass corresponds to the mass of the absorbed carbon dioxide. - Therefore, the mass of carbon dioxide produced is 0.8 g.

2. Calculate the mass of sodium carbonate formed: - The mass fraction of sodium carbonate in the solution is 1.06%. - This means that 1.06 g of sodium carbonate is present in 100 g of the solution. - Therefore, the mass of sodium carbonate formed is 1.06 g.

3. Calculate the molar mass of carbon dioxide (CO2): - The molar mass of carbon dioxide is 44.01 g/mol.

4. Calculate the moles of carbon dioxide produced: - Moles = Mass / Molar mass = 0.8 g / 44.01 g/mol ≈ 0.0182 mol.

5. Calculate the moles of sodium carbonate formed: - Moles = Mass / Molar mass = 1.06 g / (2 * 22.99 g/mol + 12.01 g/mol + 3 * 16.00 g/mol) ≈ 0.0091 mol.

6. Determine the ratio of moles of carbon dioxide to moles of sodium carbonate: - The ratio is approximately 0.0182 mol / 0.0091 mol ≈ 2.

Based on the ratio of 2, we can conclude that the alkane contains two carbon atoms. Therefore, the formula of the alkane is C2H6, which is ethane.

Please note that the calculations provided are based on the given information and assumptions made about the reaction and the products formed.