Question

Химия 11 класс. Задача на определение формулы. Пожалуйста, ОЧЕНЬ НУЖНО!!!!!! (С решением)Органическое вещество массой 16,5 г , плотность пара которого по углекислому газу 3, сожгли в струе газа, который выделился во время электролиза жидкости массой 22,5 г, аналогичной по составу и свойствам одному из продуктов горения.Второй продукт реакции в таком же количестве можно получить в результате термического разложения соли двухвалентного металла массой 92,5 г, что окрашивает пламя в красно-карминный цвет.Определите формулу вещества.

Answer 1

Ответ:

С5Н8О4

Объяснение:

Двухвалентный металл, окрашивающий пламя в карминно-красный цвет, - это стронций. Соль - карбонат стронция - в количестве 92,5:148 = 0,625 моль, термически разлагаясь по уравнению SrCO3--->SrO + CO2, даёт 0,625 моль углекислого газа CO2, в котором содержится 0,625*12 = 7,5 граммов углерода.

Электролитическое разложение воды в количестве 22,5:18 =  1,25 моль по суммарному уравнению 2H2O ---> 2H2 + O2 даст 1,25:2 = 0,625 моль кислорода и 1,25*2 = 2,5 грамма водорода.

Так как сумма масс углерода и водорода, равная 7,5 + 2,5 = 10 граммов, меньше указанной массы исследуемого вещества, в его составе есть кислород.

Соотношение количеств исследуемого вещества и кислорода равно 1:0,625:0,125 = 1:5, следовательно, в веществе содержится 5 атомов углерода, что занимает 5*12 = 60 г/моль.

Молярная масса исследуемого вещества равна 44*3 = 132 г/моль, значит, на водород и кислород в отношении 2:1 приходится 132 - 60 = 72 г/моль, откуда число атомов кислорода равно 72:(2 + 16) = 4.

Таким образом, формула исследуемого вещества имеет вид С5Н8О4.

Если говорить о структуре, то можно привести, например, формулу пентандиовой кислоты, с двумя карбоксильными группами.

Answer 2

Problem Analysis

We are given an organic substance with a mass of 16.5 g and a vapor density of 3 with respect to carbon dioxide gas. This substance is burned in a stream of gas, which is released during the electrolysis of a liquid with a mass of 22.5 g. The liquid is similar in composition and properties to one of the combustion products. Another product of the reaction, in the same quantity, can be obtained by the thermal decomposition of a salt of a divalent metal with a mass of 92.5 g, which colors the flame in a red-carmine color. We need to determine the formula of the substance.

Solution

To solve this problem, we need to analyze the given information and use the principles of stoichiometry and the properties of the substances involved.

1. Let's start by determining the molar mass of the organic substance. We can do this by dividing its mass by its vapor density. The molar mass (M) can be calculated using the formula:

M = (mass / vapor density) * M(CO2)

where M(CO2) is the molar mass of carbon dioxide (44.01 g/mol).

Plugging in the values, we get:

M = (16.5 g / 3) * 44.01 g/mol

Calculating this, we find:

M ≈ 242.75 g/mol.

2. Next, let's analyze the products of the combustion reaction. We are told that one of the products is released during the electrolysis of a liquid with a mass of 22.5 g. This liquid is similar in composition and properties to one of the combustion products. Therefore, the molar mass of this product should be the same as the molar mass of the organic substance.

3. We are also told that the other product can be obtained by the thermal decomposition of a salt of a divalent metal with a mass of 92.5 g. This product colors the flame in a red-carmine color. From this information, we can infer that the metal in the salt is responsible for the color of the flame.

4. To determine the formula of the substance, we need to find the ratio of the elements present in it. Since the molar mass of the organic substance is approximately 242.75 g/mol, we can assume that its empirical formula is the simplest whole number ratio of the elements.

5. Let's assume the empirical formula of the substance is CxHyOz. To find the values of x, y, and z, we need to determine the ratio of the elements based on the given information.

6. From the molar mass of the organic substance, we know that the molar mass of carbon (C) is approximately 12.01 g/mol. Therefore, the number of carbon atoms in one mole of the substance is given by:

n(C) = (M * x) / 12.01

where n(C) is the number of carbon atoms.

7. Similarly, the number of hydrogen (H) atoms in one mole of the substance is given by:

n(H) = (M * y) / 1.01

where n(H) is the number of hydrogen atoms.

8. The number of oxygen (O) atoms in one mole of the substance can be calculated by subtracting the sum of the number of carbon and hydrogen atoms from the total number of atoms in one mole of the substance:

n(O) = (M * z) - (n(C) + n(H))

9. Now, let's substitute the values into the equations and solve for x, y, and z.

From the given information, we know that the organic substance is burned in a stream of gas, which is released during the electrolysis of a liquid with a mass of 22.5 g. This liquid is similar in composition and properties to one of the combustion products. Therefore, the molar mass of this product should be the same as the molar mass of the organic substance.

Let's assume the molar mass of the product released during electrolysis is M1. Since the molar mass of the organic substance is approximately 242.75 g/mol, we can write:

M1 = 242.75 g/mol

Similarly, the molar mass of the product obtained by the thermal decomposition of the salt is M2. We are given the mass of the salt (92.5 g), so we can calculate the number of moles of the salt:

n(salt) = mass / molar mass = 92.5 g / M2

Since the product obtained by the thermal decomposition of the salt is in the same quantity as the other products, we can write:

M2 = M1

Substituting the value of M1, we get:

92.5 g / M2 = 92.5 g / 242.75 g/mol

Solving for M2, we find:

M2 ≈ 242.75 g/mol

Therefore, the molar mass of the product obtained by the thermal decomposition of the salt is approximately 242.75 g/mol.

10. Now that we have the molar mass of the product obtained by the thermal decomposition of the salt, we can use it to determine the empirical formula of the organic substance.

From the given information, we know that the product obtained by the thermal decomposition of the salt colors the flame in a red-carmine color. This suggests the presence of a metal in the salt that is responsible for the color.

Since the molar mass of the product obtained by the thermal decomposition of the salt is approximately 242.75 g/mol, and the molar mass of the metal is equal to its atomic mass, we can assume that the metal has a molar mass of approximately 242.75 g/mol.

By referring to the periodic table, we can find that the metal with a molar mass close to 242.75 g/mol is chromium (Cr), which has a molar mass of 51.9961 g/mol.

Therefore, the empirical formula of the organic substance is C51H99O.

Answer

The empirical formula of the organic substance is C51H99O.

Please note that this is an approximate solution based on the given information and assumptions made. The actual formula of the substance may vary depending on the exact composition and properties of the substances involved.

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