The concentration of bivalent lead ions in sample of polluted water that also contains nitrate ions is determined by adding solid sodium sulphate `(m=142)` to exacty `500mL` water 500mL` water. Calculate the molarity of kead ion if `0.355g` of solium sulphate was needed for complete precipitation of lead ions as sulphate.

If the density of some lake water is 1.25g mL^(-1) and contains 92 g of Na^+ ions per kg of water, calculate the molality of Na+ ions in the lake.

0.2 mole of HCl and 0.2 mole of barium chloride were dissolved in water to produce a 500mL solution. The molarity of the Cl- ions is :

6.2g of a sample containing Na_2CO_3, NaHCO_3 and non-volatile inert impurity on gentle heating loses 5% of its mass due to reaction 2NaHCO_3 rarr Na_2 CO_3 + H_2 O + CO_2 . Residue is dissolved in water and formed 100mL solution and its 10mL portion requires 7.5 mL of 0.2M aqueous solution of BaCI_2 for complete precipitation of carbonates. Determine mass (in gram) of Na_2 CO_3 in the original sample.

Find out % of oxalate ion in a given sample of an alkali metal oxalate salt, 0.30g of it is dissolved in 100mL water and its required 90mL of centimolar KMnO_4 solution in acidic medium :

25.3 g of sodium carbonate Na_2CO_3 is dissolved in enough water to make 250 ml of solution. If sodium carbonate dissociated completely, molar concentration of sodium ion, Na^+ and carbonate ions , CO_3^(2-) are respectively (Molar mass of Na_2CO_3=106gmol^-1) .

The 25mL of a 0.15 M solution of lead nitrate, Pb(NO_3)_2 reacts with all of the aluminium sulphate, Al_2 (SO_4)_3 , present in 20 mL of a solution. What is the molar concentration of the AI_2(SO_4)_3 + 3Pb(NO_3)_2(aq)+AI_2(SO_4)_3(aq)rarr3PbSO_4(s)+2AI(NO_3)_3(aq)