50%w∕w solution of HCl solution means that 50g of HCl is present in 100g solution. CaCO3+2HCl⟶CaCl2+H2CO3 1 mole of CaCO3 reacts with 2 moles of HCl 100g of CaCO3=1 mole of CaCO3 200g of CaCO3=2 moles of CaCO3 2 moles of CaCO3 will react with 4 moles of HCl 1 mole of HCl=36.5g of HCl 4 moles of HCl=4×36.5g of HCl=146g of HCl 50g of HCl is present in 100g solution. 146g of HCl will be present in 292g solution.