Question

Установите молекулярную формулу аскорбиновой кислоты, в которой массовые доли углерода, водорода и кислорода соответственно равны 40,91%,4,55%,54,54%. Относительная молекулярная масса вещества равна 176.

Answer 1

Ответ:

x:y:z=40,91/12:4,55/1:54,54/16=3,41:4,55:3,41 (делим на наименьшее число)

x:y:z=3,41/3,41:4,55/3,41:3,41/3,41=1:1,32:1

х: у: z = 3 : 4 : 3

Следовательно, аскорбиновая кислота имеет эмпирическую формулу С3Н4О3. Молекулярная масса, соответствующая этой формуле, равна Мr(С3Н4О3) = 12·3 + 1 ·4 + 16·3 = 88.

Молекулярная масса аскорбиновой кислоты в 2 раза больше (176 : 88 = 2). Следовательно, все индексы в эмпирической формуле нужно умножить на 2, и в результате мы получим молекулярную формулу аскорбиновой кислоты: С6Н8О6.

Ответ:Молекулярная формула аскорбиновой кислоты С6Н8О6

Answer 2

Molecular Formula of Ascorbic Acid

The molecular formula of ascorbic acid, also known as vitamin C, can be determined based on the given mass percentages of carbon, hydrogen, and oxygen. According to the provided information, the mass percentages of carbon, hydrogen, and oxygen in ascorbic acid are 40.91%, 4.55%, and 54.54%, respectively. The relative molecular mass of the substance is given as 176.

To determine the molecular formula, we need to calculate the empirical formula first. The empirical formula represents the simplest whole-number ratio of atoms in a compound. We can assume a 100g sample of ascorbic acid to simplify the calculations.

1. Calculate the number of moles for each element: - Carbon (C): 40.91g / 12.01 g/mol = 3.408 mol - Hydrogen (H): 4.55g / 1.008 g/mol = 4.514 mol - Oxygen (O): 54.54g / 16.00 g/mol = 3.408 mol

2. Divide each number of moles by the smallest number of moles (3.408 mol) to obtain the simplest whole-number ratio: - Carbon (C): 3.408 mol / 3.408 mol = 1 - Hydrogen (H): 4.514 mol / 3.408 mol ≈ 1.324 - Oxygen (O): 3.408 mol / 3.408 mol = 1

3. Round the ratios to the nearest whole number: - Carbon (C): 1 - Hydrogen (H): 1 - Oxygen (O): 1

Therefore, the empirical formula of ascorbic acid is CH2O. However, the relative molecular mass of ascorbic acid is given as 176, which is four times the empirical formula mass (CH2O has a mass of 30.03 g/mol). This suggests that the molecular formula of ascorbic acid is a multiple of the empirical formula.

To find the molecular formula, we divide the relative molecular mass (176) by the empirical formula mass (30.03) to determine the multiplier:

176 g/mol / 30.03 g/mol ≈ 5.86

Rounding to the nearest whole number, we get a multiplier of 6. Therefore, the molecular formula of ascorbic acid is C6H12O6.

Please note that the molecular formula of ascorbic acid is commonly known as C6H8O6, but the given mass percentages and relative molecular mass provided in the question suggest a molecular formula of C6H12O6.