Q.

CaCO3(s)+2HCl(aq)  CaCl2(aq)+CO2(g)+H2O(l)

Consider the above reaction, what mass of CaCl2 will be formed if 250 mL of 0.76 M HCl reacts with 1000 g of CaCO3

(Given: Molar mass of Ca, C, O, H and Cl are 40, 12, 16, 1 and 35.5 g mol-1, respectively)            [2025]

1 3.908 g  
2 2.636 g  
3 10.545 g  
4 5.272 g  

Ans.

(3)

Moles of CaCO3=Mass of CaCO3Molar mass of CaCO3=1000100mol=10mol

Moles of HCl=Molarity×Volume in L=0.76 M×0.25 L=0.19mol

CaCO3+2HCl  CaCl2+CO2+H2O

As per reaction stoichiometry, 20 mol of HCl are needed to react with 10 mol CaCO3, but only 0.19 mol of HCl is available. Thus, HCl is the limiting reagent. Moles of CaCl2 formed depends upon moles of limiting reagent i.e. HCl.

As per reaction stoichiometry, Moles of CaCl2(nCaCl2) =nHCl2 =0.192mol

Mass of CaCl2=Moles of CaCl2×Molar mass of CaCl2=0.192×111g =10.545g