chemistry (volumetric analysis

(a) Calculate the no. of mole of potassium carbonate provided
Firstly, u have to know the formula of potassium carbonate, which is K2(CO3), the mass of 1 mole of this compound would be (the Ar of K = 39.098, C = 12.011, O=15.999):
Ar = (39.098 x 2)+ (12.011+ 15.999 x 3) = 138.204g
The mass of potassium carbonate u have is 13.82. Therefore, the number of moles in ur sample would be
13.82/138.204 = 0.1 mole
bi) u have to apply this formula:
mole = conc x vol/1000
0.1 = conc x 250/1000
conc. = 0.4M

bii) The answer you got from the above is having an unit of mol/dm^3. as mentioned , 1 mole of substance has mass of 138.2g, 0.4 mole would have mass of 55.2816g. THis means that the concentration of the solution would be 55.2816g/dm^3
ci) the mole of sample u were given was 0.1mole, using the formula of
mole = conc x vol/1000
0.1 = 0.25 x vol/1000
vol = 400cm^3
when u answer this question, try to input the values into the calculator=]