calculate the number of mole of cacl that can be obtained from 30g of caco3 in the presence of excess Hcl(Ca =40,C=12,O=16,H=1,Cl=355)

Answer 1

You mean Cl = 35.5 g/mol but we do not need it
CaCO3 = 40 +12 + 3*16 = 100 g/mol
so 30/100 = 0.30 mol of CaCO3
same number of mols of CaCl because Ca has to be the same number of atoms left and right
so you get 0.30 mol of CaCl

Answer 2

You probably know better and you're just lazy but you really need to learn to post/type better questions. That's HCl, CaCl2, CaCO3, Cl is 35.5 etc.
CaCO3 + 2HCl --> CaCl2 + H2O + CO2
mols CaCO3 = grams/molar mass = 30.0/100 = 0.300 mol
From the equation you can see we get 1 mol CaCl2 for every 1 mol CaCO3; therefore, we should expect 0.3 mol CaCl2 from 0.3 mol CaCO3.