Question

Найти молекулярную формулу углеводорода, если известно, что относительная плотность паров углеводорода по водороду равна 49, массовая доля углерода в нем равна 85,71%, водорода равна 14,29%

Answer 1

Дано:
__________
n(C)=w * Mr(CnHm) / M(C)
Mr(CnHm)=2*49=98
n(C)=0,8571*98/12=7
n(H)=0,1429*98/1=14
_____
Ответ: C7H14 (гептан)

Answer 2

Finding the Molecular Formula of the Hydrocarbon

To find the molecular formula of the hydrocarbon, we can use the given information about the relative density of the hydrocarbon vapor to hydrogen and the mass percentages of carbon and hydrogen in it.

The relative density of the hydrocarbon vapor to hydrogen is given as 49, and the mass percentage of carbon is 85.71% while the mass percentage of hydrogen is 14.29%.

Using this information, we can calculate the molecular formula of the hydrocarbon.

Calculation

First, we need to find the empirical formula of the hydrocarbon using the mass percentages of carbon and hydrogen.

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

The empirical formula can be calculated using the following steps: 1. Convert the mass percentages of carbon and hydrogen to moles. 2. Divide the moles of each element by the smallest number of moles obtained. 3. Use the resulting ratios to write the empirical formula.

Let's proceed with the calculation.

The molar ratio of carbon to hydrogen in the empirical formula can be calculated using the mass percentages provided.

The molar ratio of carbon to hydrogen can be calculated as follows: - For carbon: \( \frac{85.71}{12} \) - For hydrogen: \( \frac{14.29}{1} \)

After obtaining the molar ratios, we can simplify them to find the empirical formula.

Empirical Formula Calculation

The molar ratio of carbon to hydrogen is approximately 7.14:14.29, which simplifies to 1:2.

Therefore, the empirical formula of the hydrocarbon is CH2.

Conclusion

The molecular formula of the hydrocarbon can be determined by finding the multiple of the empirical formula that matches the given relative density. However, without additional information, it is not possible to determine the specific molecular formula of the hydrocarbon.

Note: The specific molecular formula of the hydrocarbon cannot be determined without additional information such as the molar mass of the hydrocarbon or the molecular weight of the compound.