Short Answer TypeCalculate the mass of sodium acetate (CH3COONa) required to make 500 mL of 0·375 molar aqueous solution. Molar mass of sodium acetate is 82·0245g mol–1.
The density of 3M solution of NaCl is 1.25g ml-1. Calculate molality of the solution.
In a reaction vessel 0.184 g of NaOH is required to be added for completing the reaction. How many millilitre of 0.150 M NaOH solution should be added for this requirement?
Long Answer TypeCommercially available concentrated hydrochloric acid contains 38% HCl by mass.
(i) What is the molarity of the solution (density of solution = 1·19g cm-3)?
(ii) What volume of concentrated HCl is required to make 1·0L of 0·10 M HCl?
Short Answer TypeLong Answer TypeCalculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040.(assume the density of water to be one).
Short Answer TypeCalculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL–1 and the mass per cent of nitric acid in it being 69%.
Determine the molecular formula of an oxide of iron in which the mass per cent of iron and oxygen are 69.9 and 30.1 respectively.
We have given,
Mass percent of iron (Fe) =69.9%
Mass percent of oxygen (O)=30.1%
Number of moles of iron present in the oxide =69.90/55.85 =1.25
Number of moles of oxygen present in the oxide=30.1/16.0
=1.88
Ratio of iron to oxygen in the oxide,
1.25:1.88
=1:1.5
=2:3
Therefore the empirical formula of the oxide is Fe2O3.
Empirical formula mass of Fe2O3= [2(55.85) +3(16)]g
Molar mass of Fe2O3=159.69g
Thus, n= Molar mass/Empirical Formula mass =159.69/159.7g
=0.999 = 1(approx.)
Molecular formula of a compound is obtained by multiplying the empirical formula with n. Thus, the empirical formula of the given oxide is Fe2O3 and n is 1.
Hence, the molecular formula of the oxide is Fe2O3.
Long Answer TypeA sample of drinking water was found to be severely contaminated with chloroform, CHCl3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).
(i) Express this is percent by mass.
(ii) Determine the molality of chloroform in the water sample.
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