Complete and balance the following equation:

$$Cr_2O_7^{2-}$$ + C₂H₄O $$\to$$ C₂H₄O₂ + Cr³⁺

The density of a 3 M Sodium thiosulphate solution (Na₂S₂O₃) is 1.25 g per ml. Calculate

(i) the percentage by weight of sodium thiosulphate,

(ii) the mole fraction of sodium thiosulphate and

(iii) the molalities of Na⁺ and $$S_2O_3^{-2}$$ ions

3 g of a salt of molecular weight 30 is dissolved in 250 g of water. The molality if the solution is _____.

4.08 g of a mixture of BaO and an unknown carbonate MCO₃ was heated strongly. The residue weighed 3.64 g. This was dissolved in 100 ml of 1 N HCl. The excess acid required 16 ml of 2.5 N NaOH solution for complete neutralization. Identify the metal M. (At wt. H = 1, C = 12, O = 16, Cl = 35.5, Ba = 138)