Question

QUESTION ❓✔️❓

•Carbohydrates are Compunds containing only carbon, hydrogen and oxygen.
When heated in the absence of air these compound decomposes to form carbon and water.
If 310 gram of a carbohydrate leave residue of 124 g of carbon on heating in absence of air , what is empirical formula of the carbohydrates ?


• Calculate mole fraction of HCL in a solution containing 24.8 percent of HCL by mass ? ​

Answer 1

24.8 g HCl in 100 g of water. So, mass of HCl= 24.8g and mass of water = 100-24.8 = 75.2 g. Hence , mole fraction of HCl in the given solution is 0.139.

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Answer 2

Question 1)

Given :-

Mass of carbohydrate = 310g

Mass of carbon = 124g

To Find :-

Empirical formula of the carbohydrate

Solution :-

Mass of water = 310 - 124 = 186

No of moles of carbon = 124/12 = 10.33

No of moles of water = 186/18 = 10.33

Their ratio :-

➟ C : H₂O

➟ 10.33 : 10.33

➟ 1 : 1

Empirical formula :- CH₂O

Question 2)

Given :-

Mass of HCl = 24.8g

To Find :-

Mole fraction

Solution :-

Molecular mass of HCl = 1 + 35.5 = 36.5g

Mass of water = 100 - 24.8 = 75.2g

Molecular mass of water = 2 × 1 + 16 = 18g

No of moles of HCl = 24.8/36.5 = 0.68

No of moles of water = 75.2/18 = 4.2

Mole fraction :-

➟ No of moles of HCl/No of moles of HCl + No of moles of H₂O

➟ 0.68/0.68 + 4.2

➟ 0.68/4.88

➟ 0.139