Question

an alloy of metal A and B in the eatio of 2:5 and weighs 36g the percentage of metal A is 22.22% if atomic mass of A is 40 then atomic mass of metal B is

Answer 1

If %A = 22.22%, then %B = 77.78.
Take 100 g sample to give you
22.22 g A
77.78 g B.
Convert to mols.
22.22/40 = 0.5555 mols A.
77.78/atomic mass B = ? mols B.
You know the ratio is A2B5; re-write this way letting X stand for atomic mass of B.
22.22/40 = 0.5555 x some # = 2
77.78/X = ? x some # = 5
We can calculate "some # from A.
2/0.5555 = 3.60 and we use that number to calculate ? from B. That will be 5/3.60 = 1.388. Now the B line reads
77.78/X = ? x 1.388 which allows us to calculate X as 77.78/1.388 = 56 for the atomic mass of B.

Check: If A2B5 is correct.
2*40 = 80
5*56 = 280
molar mass A2B5 = 360
%A = [80/360]*100 = 22.22
%B = [280/360]*100 = 77.78
Looks ok to me.