?$ (1) $?解：已知每片鈣片質(zhì)量為?$1.25\ \mathrm {g}，$?每片含?$CaCO_{3} 0.625\ \mathrm {g}。$?
根據(jù)質(zhì)量分?jǐn)?shù)公式?$ =\frac {m_{溶質(zhì)}}{m_{溶液}}×100\%($?這里?$m_{溶質(zhì)}$?為?$CaCO_{3}$?質(zhì)量，?$m_{溶液}$?為鈣片質(zhì)量?$)，$?
則?$CaCO_{3}$?的質(zhì)量分?jǐn)?shù)?$ ({CaCO_{3}})=\frac {0.625\ \mathrm {g}}{1.25\ \mathrm {g}}×100\%=50\%。$?
?$ (2) $?根據(jù)化合物中某元素質(zhì)量分?jǐn)?shù)公式?$ =\frac {Ar(元素)×n}{Mr(化合物)}×100\%$?
則?$ (\mathrm {Ca})=\frac {40}{100}×100\%=40\%。$?
每片含?$CaCO_{3} 0.625\ \mathrm {g}，$??$CaCO_{3}$?中鈣元素質(zhì)量分?jǐn)?shù)為?$40\%，$?
則每片鈣片中鈣元素質(zhì)量?$m(\mathrm {Ca})=0.625\ \mathrm {g}×40\%=0.25\ \mathrm {g}。$?
鈣片質(zhì)量為?$1.25\ \mathrm {g}，$?所以鈣片中鈣元素質(zhì)量分?jǐn)?shù)?$ _{鈣}=\frac {0.25\ \mathrm {g}}{1.25\ \mathrm {g}}×100\%=20\%。$?
?$ (3) $?每次一片，每天兩次，每片鈣片中鈣元素質(zhì)量為?$0.25\ \mathrm {g}($?由?$(2)$?已算出?$)。$?
則每天補充鈣元素質(zhì)量?$m=0.25\ \mathrm {g}×2=0.5\ \mathrm {g}。$?
綜上；?$(1) $?鈣片中?$CaCO_{3}$?的質(zhì)量分?jǐn)?shù)為?$50\%；$??
$(2) CaCO_{3}$?中鈣元素質(zhì)量分?jǐn)?shù)為?$40\%，$?鈣片中鈣元素質(zhì)量分?jǐn)?shù)為?$20\%；$
??$(3) $?每天能補充的鈣元素為?$0.5\ \mathrm {g}。$?
