The reaction for formation of CuCl2 is as follows ;
CuCO3 + 2HCl —> CuCl2 + H2O + CO2
The stoichiometry of CuCO3 to CuCl2 is 1:1
Mass of CuCl2 to be produced - 11.0 g
Number of moles of CuCl2 -11.0 g / 134.5 g/mol = 0.082 mol
According to stoichiometry the number of CuCO3 moles required = 0.082 mol
Therefore mass of CuCO3 required = 0.082 mol x 123.5 g/mol = 10.13 g