引用樓主倚天之劍於2009-03-19 18:27發表的 化學唔同科學- - :
把6.30g的二元酸H2X溶於水,製成250.0cm^3的溶液.要完全中和25.0cm^3的酸溶液,需用20.0cm^3的0.500M的氫氧化鉀溶液.計算:
a) 該二元酸的相對分子質量;
b) X的相對原子質量.
no. of moles of KOH = 0.500 x 20/1000 = 0.01mol
H
+ + OH
- -> H2O
mole ratio of H
+:OH
- = 1:1
no. of moles of H
+ in 25.0cm
3 of acid = 0.01mol
no. of moles of H
+ in 250.0cm
3 of acid = 0.01 x 250/25 = 0.1mol
mole ratio of H
+ to H2X = 2:1
no. of moles of H
2X = 0.1/2 = 0.05
relative molecular mass of H
2X = 6.30/0.05 = 126.0
relative atomic mass of X = 126.0 - 2 x 1.0 = 124.0