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Some Basic Concepts of Chemistry

Long Answer Type

151. Fe₂(SO₄)₃ is the empirical formula of a crystalline compound of iron. It is used in water and sewage treatment for the removal of suspended impurities. Calculate the mass percentage of iron, sulphur and oxygen in the compound.

Molecular mass of

Percentage of iron

Percentage of sulphur

Percentage of oxygen

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Short Answer Type

152.

What is the empirical formula of the compounds having molecular formula as:
(i) C₆H₆
(ii) C₆H₁₂(iii) H₂O₂
(iv) H₂O
(v) Na₂CO₃(vi) B₂H₆(vii) N₂O₆

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153. Determine the empirical formula of an oxide of iron which has 69·9% iron and 30.1% dioxygen by mass.

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Long Answer Type

154.

Silicon (Si = 28) forms a compound with chlorine (Cl = 35·5) in which 5·6g of silicon is combined with 21·3g of chlorine. Calculate the empirical formula of the compound.

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155.

2.38 g of uranium was heated strongly in a current of air. The resulting oxide weighed 2806 g. Determine the empirical formula of the oxide. (At. mass of U = 238, O = 16).

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156.

Four grams of copper chloride on analysis was found to contain 1·890 g of copper (Cu) and 2·110 g of chlorine (Cl). What is the empirical formula of copper chloride?

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157. The atomic mass of metal M is 56. Calculate the empirical formula of its oxide containing 70% of M.

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158. A chemical compound is found to have the following composition: C = 19·5%, Fe = 15·2%, N = 22·8%, K = 41·5%. Calculate the empirical formula of the compound. What will be the molecular formula if the molecular mass of the compound is 368? Name the compound also.

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159.

A compound on analysis, is found to have the following composition:
(i) Sodium = 14·31%, (ii) Sulphur = 9·97
(iii) Oxygen = 69·50% (iv) Hydrogen = 6·22%.
Calculate the molecular formula of the compound assuming that whole of hydrogen in the compound is present as water of crystallisation. Molecular weight of the compound is 322.

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