1.1400g
設(shè)需要加水的質(zhì)量是x.
100*30%=(100+x)*2%
x=1400g

2.設(shè)200g廢水中NaOH的質(zhì)量是x,反應(yīng)生成NaCl的質(zhì)量是y.
消耗HCl的溶質(zhì)質(zhì)量是73*2%=1.46g
NaOH+HCl=NaCl+H2O
40 36.558.5
x 1.46gy

40/x=36.5/1.46=58.5/y
x=1.6g
y=2.34g
廢水中氫氧化鈉的質(zhì)量分?jǐn)?shù)是1.6/200*100%=0.8%
反應(yīng)后所得到的溶液的質(zhì)量是200+73=273g,溶質(zhì)的質(zhì)量分?jǐn)?shù)是2.34/273*100%=0.86%

答：1.廢水中氫氧化鈉的質(zhì)量分?jǐn)?shù)是0.8%
2.反應(yīng)后所得到的溶液中溶質(zhì)的質(zhì)量分?jǐn)?shù)是0.86%