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Question

How much H2 is obtained when steam is passed over 21 g red hot iron? What would be the volume of that H2 at STP? [Fe=56] [2+1]

OR

SO3 is prepared by oxidising SO2 in presence of O2. How much SO2 in grams will be required to produce 40 g of SO3? (S = 32, O = 16)

WBBSE Class X Physical Science Chemical Calculations 03 Mark 2024

Answer

Balanced Eq: 3Fe + 4H2O → Fe3O4 + 4H2

.                  3 × 56 g  = 168 g                  4 × 2 = 8 g

Amount of H2 produced by 168 g of Fe = 8 g

or, Amount of H2 produced by 21 g of Fe = 8\over168 × 21 g = 1 g

Volume of 2 g of H2 = 22.4 liters

∴ Volume of 1 g of H2 = 22.4 / 2 = 11.2 liters

OR

Balanced Eq: 2SO2 + O2 → 2SO3

.                             64 g    32 g     80 g

To produce 80 g of SO3, 64 g of SO2 is required.

∴ To produce 40 g of SO3, 32 g of SO2 is required.

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