# Solve the following problem: Carbohydrates are compounds containing only carbon, hydrogen, and oxygen. When heated in the absence of air, these compounds decompose to form carbon and water. - Chemistry

Sum

Solve the following problem:

Carbohydrates are compounds containing only carbon, hydrogen, and oxygen. When heated in the absence of air, these compounds decompose to form carbon and water. If 310 g of a carbohydrate leaves a residue of 124 g of carbon on heating in absence of air, what is the empirical formula of the carbohydrate?

#### Solution

Given: Mass of carbon residue = 124 g, mass of carbohydrate = 310 g

To find: Empirical formula of the carbohydrate

Calculation: Since the 310 g of compound decomposes to carbon and water and the mass of carbon produced is 124 g, the remaining mass would be of water.

∴ Mass of water = 310 – 124 = 186 g

Moles of C = "Mass of C"/"Atomic mass of C"=124/ 12 = 10.33 mol

Moles of water = "Mass of water"/"Molar mass of water"=186/18 = 10.33 mol

The ratio of number of moles of C : water = C : H2O = 1 : 1

Hence, empirical formula = CH2O

Empirical formula of the carbohydrate = CH2O

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#### APPEARS IN

Balbharati Chemistry 11th Standard Maharashtra State Board
Chapter 2 Introduction to Analytical Chemistry
Exercises | Q 4. (M) | Page 25