Question

12．將20g的銅鋅合金投入到足量的稀硫酸中，充分反應(yīng)，放出氣體的質(zhì)量為0.2g．計算合金中銅的質(zhì)量分?jǐn)?shù)．（反應(yīng)的化學(xué)方程式：Zn+H₂SO₄═ZnSO₄+H₂↑）

Answer 1

分析 根據(jù)鋅與稀硫酸的反應(yīng)生成的氫氣的質(zhì)量求出鋅的質(zhì)量，即可求出合金中銅的質(zhì)量分?jǐn)?shù)．

解答 解：設(shè)樣品中鋅的質(zhì)量為X
Zn+H₂SO₄═ZnSO₄+H₂↑
65                 2
X                0.2g                                             
$\frac{65}{X}$=$\frac{2}{0.2g}$                                                        
X=6.5g                                                            
銅的質(zhì)量分?jǐn)?shù)是
$\frac{20g-6.5g}{20g}$×100%=67.5%                                           
答：樣品中銅的質(zhì)量分?jǐn)?shù)為67.5%

點評 本題屬于根據(jù)化學(xué)方程式的簡單計算，注意計算的數(shù)據(jù)的準(zhǔn)確性即可．