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Chemistry

Some Basic Concepts of Chemistry Mass and Stoichiometry

Chemistry > Chapter: Some Basic Concepts of Chemistry > Mass and Stoichiometry

Chapter: Some Basic Concepts of Chemistry

Mass and Stoichiometry
Question 1 2.5 moles of sulphuryl chloride were dissolved in water to produce sulphuric acid and hydrochloric acid. How many moles of KOH will be required to completely neutralize the solution? Ans. SO 2Cl2 + 2H2O H2SO 4 + 2HCl

Mol of HCl produced from 2.5 moles of SO2 Cl2 = 5 mol Mol of H2SO 4 produced from 2.5 moles of SO2Cl2 = 2.5 mol H2SO4 + 2KOH HCl + KOH K2SO 4 + 2H2O; KCl + H2 O

Now, 5 mol of H2SO 4 require KOH = 2.5 mol Total KOH required = 10 + 2.5 = 12.5 mol.

Question 2 Two acids H2SO4 and H3PO4 are neutralized separately by the same amount of an alkali when sulphate and dihydrogen orthophosphate are formed respectively. Find the ratio of masses of H2SO4 and H3PO4 [at mass P = 31] Ans.

H2SO4 + 2NaOH Na 2SO4 + 2H2O H3PO4 + NaOH NaH2PO4 + H2O Equivalent of alkali = 1 g equivalent of H2SO4 = 1 g equivalent of H3PO4 The two acids must react in the ratio of their equivalent masses. Equivalent mass of H2SO4 = Equivalent mass of H3PO4 = Hence ratio of masses of H2SO4: H3PO4 = 49:98 =1:2. Question 3 What is the mass of 2 litre sample of water containing 25% heavy water (D2O) in it by volume? Density of water is 1.0 g cm-3 where as that of D2O is 1.06 g cm-3. Ans.

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Question 4 Differentiate between molar mass and equivalent mass of a substance? Ans.

The mass of one mole of particles is called molar mass. The number of entities (atoms or molecules) contained in a molar mass is equal to 6.023 ×1023. The number of parts by weight of a substance that combines with or displaces 1.008 parts by weight of hydrogen or 8.0 parts of oxygen or 35.5 parts of chlorine is called its equivalent weight. Or the quantity of a substance in grams numerically equal to its equivalent weight is called its gram equivalent weight. Question 5 What is the amount of copper obtained from 100 g of copper sulphate? (Atomic mass of Cu = 63.5 u) Ans.

Question 6 How many grams of oxygen (O2) are required to completely react with 0.200 g of hydrogen (H2) to yield water (H2O)? Ans. The balanced equation for the reaction is:

4 g of H2 requires oxygen = 32g

0.200 g of H2 requires oxygen =

Question 7 What is the vapour density of a gas if its molecular mass is 22? Ans. Molecular mass = 2 vapour density = 2 22 = 44.

Question 8 What is the atomic weight of an element whose specific heat is 0.214 cal/gm? Ans.

According to Dulong pettits law, Atomic heat capacity of elements (metals) = 6.4 cal mol-1 = gram atomic...