(Relative atomic masses:H=1.0,O=16.0,Na=23.0,Mg=24.0,S=32.0,Cl=35.5,K=39.0)
A . sodium hydroxide
B . potassium nitrate
C . magnesium chloride
D . sodium sulphate
更新1:
explanation is required
mole concept & calculation
2009-06-06 8:26 pm
The ocncentrations of the following four solutions are all 1g/dm^3.Which of the solutions contains the greatest number of ions per dm^3?
(Relative atomic masses:H=1.0,O=16.0,Na=23.0,Mg=24.0,S=32.0,Cl=35.5,K=39.0)
A . sodium hydroxide
B . potassium nitrate
C . magnesium chloride
D . sodium sulphate
(Relative atomic masses:H=1.0,O=16.0,Na=23.0,Mg=24.0,S=32.0,Cl=35.5,K=39.0)
A . sodium hydroxide
B . potassium nitrate
C . magnesium chloride
D . sodium sulphate
回答 (1)
2009-06-06 9:59 pm
✔ 最佳答案
The answer is A.
Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol
Molar mass of KNO3 = 39 + 14 + 16x3 = 101 g/mol
Molar mass of MgCl2 = 24 + 35.5x2 = 95 g/mol
Molar mass of Na2SO4 = 23x2 + 32 + 16x4 = 142 g/mol
Avogadro constant = L /mol
A.
Molarity of NaOH = 1/40 mol/dm3
Each mol of NaOH contains 2 mol of ions (1 mol Na+ and 1 mol OH-).
No. of ions per dm3 = (1/40) x 2 x L = 0.05L ions/dm3
B.
Molarity of KNO3 = 1/101 mol/dm3
Each mol of KNO3 contains 2 mol of ions (1 mol K+ and 1 mol NO3-).
No. of ions per dm3 = (1/101) x 2 x L = 0.0198L ions/dm3
C.
Molarity of MgCl2 = 1/95 mol/dm3
Each mol of MgCl2 contains 3 mol of ions (1 mol of Mg2+ and 2 mol of Cl-).
No. of ions per dm3 = (1/95) x 3 x L = 0.0316L ions/dm3
D.
Molarity of Na2SO4 = 1/142 mol/dm3
Each mol of Na2SO4 contains 3 mol of ions (2 mol Na+ and 1 mol SO42-).
No. of ions per dm3 = (1/142) x 3 x L = 0.0211L ions/dm3
The greatest ions per dm3 is A (0.05L ions/dm3).
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