1. 25.0 cm cube of distilled water is pipetted into a conical flask. 5.85g of sodium chloride is hen added into the conical flask. The concentration of sodium chloride soluion is
A. 0.04M
B. 0.4
C. 4.0M
D. unknown
2. Hydrated oxalic acid has the formula H2C2O4•2H2O. 5.04g of oxalic acid dihydrate crystals were used. 我想問如果要計number of moles of oxalic acid, 需唔需要考慮埋water of crystallization?
form 4 化學ｍｃ
2007-09-05 1:45 am
回答 (2)
2007-09-05 4:29 am
✔ 最佳答案
1. Standard atomic weight : Na = 22.99, Cl = 35.45 No. of mole of NaCl = 5.85 / (22.99 + 35.45) = 0.100 mol.
Volume of solution in dm³ = 25 / 1000 = 0.025 dm³
Concentration of NaCl solution = 0.100 / 0.025 = 4.0M
2. 要.
2007-09-05 11:39 pm
1. C. 4.0 M
molar mass of NaCl = 23+35.5 = 58.5
no. of moles of NaCl = 5.85 / 58.5 = 0.1
concentration = no. of moles / volume
= 0.1 / 0.025
= 4M
So answer is C
2. YES!
because the mass given include mass of water
You have to subtract the mass of water first in order to get the mass of oxalic acid
then you use the real mass of oxalic acid / molar mass of oxalic acid
you can get no. of moles of oxalic acid
If you want, I can calculate the answer for you as well
please make a remark if you want so
molar mass of NaCl = 23+35.5 = 58.5
no. of moles of NaCl = 5.85 / 58.5 = 0.1
concentration = no. of moles / volume
= 0.1 / 0.025
= 4M
So answer is C
2. YES!
because the mass given include mass of water
You have to subtract the mass of water first in order to get the mass of oxalic acid
then you use the real mass of oxalic acid / molar mass of oxalic acid
you can get no. of moles of oxalic acid
If you want, I can calculate the answer for you as well
please make a remark if you want so
收錄日期: 2021-04-13 13:18:12
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