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A is a solution containing 3.56g of Na2CO3.XH20 in 500cm cube of a solution. b is 0.05 mole per dm cube solution of H2SO4. b was put in a burette and titrated against 25cm cube portions of a using methyl orange as indicator. an average titre of 20.00 cm cube was recorded. H2SO4 +na2co3.xh2o -------> NA2SO4 + CO2 + (x+1)h2orna) Calculate the concentration of NA2CO3.xH2O in a in mole per dm cube.
Accepted Answer
a) Calculate the concentration of Na2CO3.xH2O in A in mole per dm cube.
思路：
1、根据平衡化学方程式，得到 1 mol H2SO4 对应 1 mol Na2CO3.xH2O。
2、已知 H2SO4 的浓度和体积，可求得反应的 H2SO4 的摩尔数，即为 Na2CO3.xH2O 的摩尔数。
3、根据 Na2CO3.xH2O 的质量和体积，可求得其物质的浓度。
计算：
1 mol H2SO4 对应 1 mol Na2CO3.xH2O
0.05 mol/dm3 × 20.00 cm3 / 1000 cm3/dm3 = 0.001 mol H2SO4
质量守恒定律：
3.56 g Na2CO3.xH2O / 106 g/mol = 0.0336 mol Na2CO3.xH2O
浓度 = 摩尔数 / 体积
0.0336 mol / 0.5 dm3 = 0.0672 mol/dm3
因此，Na2CO3.xH2O 在 A 中的浓度为 0.0672 mol/dm3。
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