1. A mixture containing zinc oxide and excess carbon powder was heated in a crucible as seen in the following diagram.
Data collected in this experiment are listed in the following table:
crucible---23.8g
crucible and mixture before heating---32.8g
crucible and mixture after heating---30.6g
a.) Write a chemical equation for the reaction of zinc oxide and carbon.
b.) Find the number of moles of CO2 formed.
c.) Find the number of moles of ZnO in the mixture.
2.) Compound X has the following percentage composition by mass:
Fe--- 20.1% composition by mass
S--- 11.5% composition by mass
H--- 5.1% composition by mass
O--- 63.3% composition by mass
a.) Find the empirical formula of X.
b.) It is found that compound X conatins water of crystallisation. How will you test for the presence of water of crystallisation? State any expected observable change.
c.) Suggest the formula of X in which the ions and water of crystallisation are clearly shown.
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chem LQ (ans in full solution)
2010-04-06 12:51 am
回答 (2)
2010-04-06 1:19 am
✔ 最佳答案
1. a.)
2ZnO + C → 2Zn + CO2
b.)
Mass of CO2 formed = 32.8 - 30.6 = 2.2 g
No. of moles of CO2 formed = 2.2/(12 + 16x2) = 0.05 mol
c.)
No. of moles of ZnO in the mixture = 0.05 x 2 = 0.1 mol
2.)
a.)
Mole ratio Fe : S : H : O
= (20.1/56) : (11.5/32) : (5.1/1) : (63.3/16)
= 0.359 : 0.359 : 5.1 : 3.96
= 1 : 1 : 14 : 11
Empirical formula of X = FeSH14O11
b.)
Water can change anhydrous cobalt(II) chloride paper from blue to pink.
(or: Water can change anhydrous copper(II) sulphate from white to blue.)
c.)
Assume that all the 14 H atoms are in the water of crystallization (H2O).
No. of O atoms in the water of crystallization = 14 x (1/2) = 7
No. of O atoms in the anhydrous salt = 11 - 7 = 4
Formula of X = FeSO4•7H2O
(FeSO4 contains Fe^2+ and SO4^2- ions.)
2010-04-10 19:54:50 補充：
尊重知識產權，請樓下註明是抄襲 (copy and paste) 在下。
並敬請不要稱呼在下為「no」。
參考: 胡雪八
2010-04-08 10:32 pm
1.
a.)
2ZnO + C → 2Zn + CO2
b.)
Mass of CO2 formed = 32.8 - 30.6 = 2.2 g
No. of moles of CO2 formed = 2.2/(12 + 16x2) = 0.05 mol
c.)
No. of moles of ZnO in the mixture = 0.05 x 2 = 0.1 mol
2.)
a.)
Mole ratio Fe : S : H : O
= (20.1/56) : (11.5/32) : (5.1/1) : (63.3/16)
= 0.359 : 0.359 : 5.1 : 3.96
= 1 : 1 : 14 : 11
Empirical formula of X = FeSH14O11
b.)
Water can change anhydrous cobalt(II) chloride paper from blue to pink.
(or: Water can change anhydrous copper(II) sulphate from white to blue.)
c.)
Assume that all the 14 H atoms are in the water of crystallization (H2O).
No. of O atoms in the water of crystallization = 14 x (1/2) = 7
No. of O atoms in the anhydrous salt = 11 - 7 = 4
Formula of X = FeSO4•7H2O
(FeSO4 contains Fe^2+ and SO4^2- ions.)
a.)
2ZnO + C → 2Zn + CO2
b.)
Mass of CO2 formed = 32.8 - 30.6 = 2.2 g
No. of moles of CO2 formed = 2.2/(12 + 16x2) = 0.05 mol
c.)
No. of moles of ZnO in the mixture = 0.05 x 2 = 0.1 mol
2.)
a.)
Mole ratio Fe : S : H : O
= (20.1/56) : (11.5/32) : (5.1/1) : (63.3/16)
= 0.359 : 0.359 : 5.1 : 3.96
= 1 : 1 : 14 : 11
Empirical formula of X = FeSH14O11
b.)
Water can change anhydrous cobalt(II) chloride paper from blue to pink.
(or: Water can change anhydrous copper(II) sulphate from white to blue.)
c.)
Assume that all the 14 H atoms are in the water of crystallization (H2O).
No. of O atoms in the water of crystallization = 14 x (1/2) = 7
No. of O atoms in the anhydrous salt = 11 - 7 = 4
Formula of X = FeSO4•7H2O
(FeSO4 contains Fe^2+ and SO4^2- ions.)
參考: no
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