[" 3"," 20.How many unit cells are present in a cube "],[" 5"," Xhaped ideal crystal of NaCl of mass "1.00g" ? "],[" [Atomic masses: "Na=23,Cl=35.5]],[" (a) "2.57times10^(21)," b) "5.14times10^(21)],[" c) "1.28times10^(21)," d) "1.71times10^(21)]