chem 問題(F.6頭)

2010-08-25 5:45 am

Oxygen can be converted to ozone by passing a high voltage across the gas.

-->would the mass of the gas be changed after the convertion?Explain your answer.

更新1:

Find the mass of metal and water of crystallization in(1)100g of Na2SO4.10H2O.

更新2:

但mass of metal 唔係只指Na 咩?!

回答 (1)

*Benny*

2010-08-26 6:16 am

✔ 最佳答案

1,the mass will not change since conservation of mass i.e. O2--->2/3O3 mass of O2=mass of O3 formed but as the convertion is an endothermic reaction, so the volume of O3 is greater than that of O2
2,mole of Na2SO4.10H2O=100g/(23x2+32.1+16x4+18x10)gmol^-1=0.31mol
as Na2SO4.10H2O-->Na2SO4 + 10H2O
mole of H2O = 0.31molx10=3.1mol
mass of H2O=3.1molx18gmol^-1=55.8g
hence mass of Na2SO4=100-55.8=44.2g
hope that i can help u

2010-08-26 12:35:42 補充：
Na2SO4 exists as metallic compound so i think the question should asking for the Na2SO4(2Na+ + (SO4)2-) these are ions! hence it is impossible to find the mass of the Na metal

2010-08-27 18:36:34 補充：
或者用以咁睇
percentage of Na = 23x2g/(23x2+32.1+16x4+18x10)gmol^-1 x 100% = 14.3%
therefore the mass of Na = 14.3% x 100g = 14.3 g

參考: my chem knowledge

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