Question

Визначте молекулярну формулу вуглеводню, якщо внаслідок спалювання 1,12 г цього вуглеводню утворилося 1,792 л вуглекислого газу (н.у.) і 1,44 г води, а відносна густина його за гелієм дорівнює 28.

Answer 1

 Общаться в чатеn(CO2)=1.792/22.4=0.08 n©=0.08 m©= 0.08*12=0.96гn(H2O)=1.44/18=0.08 n(H)=0.16 m(H)=1.16г0.96+1.16=1.12гC:H=0.08:0.16  или     8:16M= 28*4=112г/мольОтвет: С8Н16

Answer 2

Molecular Formula of the Hydrocarbon

To determine the molecular formula of the hydrocarbon, we need to analyze the products of its combustion. According to the information provided, 1.12 g of the hydrocarbon produced 1.792 L of carbon dioxide (at standard temperature and pressure) and 1.44 g of water. Additionally, the relative density of the hydrocarbon with respect to helium is given as 28.

To find the molecular formula, we can follow these steps:

1. Calculate the number of moles of carbon dioxide produced: - The molar mass of carbon dioxide (CO2) is 44.01 g/mol. - Using the given volume of 1.792 L, we can convert it to moles using the ideal gas law: PV = nRT. - Assuming standard temperature and pressure (STP), the value of R is 0.0821 L·atm/(mol·K). - Plugging in the values, we get: (1 atm) * (1.792 L) = n * (0.0821 L·atm/(mol·K)) * (273.15 K). - Solving for n, we find that the number of moles of carbon dioxide is approximately 0.081 mol.

2. Calculate the number of moles of water produced: - The molar mass of water (H2O) is 18.02 g/mol. - Using the given mass of 1.44 g, we can convert it to moles: 1.44 g / 18.02 g/mol ≈ 0.08 mol.

3. Determine the empirical formula: - The empirical formula represents the simplest whole number ratio of atoms in a compound. - To find the empirical formula, we need to determine the ratio of carbon to hydrogen in the hydrocarbon. - From the combustion reaction, we know that the carbon in the hydrocarbon is converted to carbon dioxide, and the hydrogen is converted to water. - The ratio of carbon to hydrogen can be found by dividing the number of moles of carbon dioxide by the number of moles of water: 0.081 mol CO2 / 0.08 mol H2O ≈ 1.01. - This ratio suggests that there is approximately 1 carbon atom for every 1 hydrogen atom in the hydrocarbon.

4. Determine the molecular formula: - To find the molecular formula, we need to know the molar mass of the hydrocarbon. - The relative density of the hydrocarbon with respect to helium is given as 28. - The molar mass of helium is approximately 4 g/mol. - The relative density is the ratio of the molar mass of the hydrocarbon to the molar mass of helium: 28 = Molar mass of hydrocarbon / 4. - Solving for the molar mass of the hydrocarbon, we find that it is approximately 112 g/mol.

- Since the empirical formula indicates a 1:1 ratio of carbon to hydrogen, and the molar mass of the hydrocarbon is approximately 112 g/mol, we can conclude that the molecular formula of the hydrocarbon is C4H4.

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