neutralization and salt

Ellen

2008-04-13 5:03 am

Alvin is helping his father to prepare a fertilizer solution for a large potted
plant. He is given a bottle of 0.5M NH4NO3 and a bottle of 0.5M HCl.
His father reminds him that the fertilizer solution should have the following
composition:
Nitrogen 2g
Potassium 1g
Volume of solution 250cm3
Alvin plans to mix Xcm3 of 0.5M NH4NO3, Ycm3 of 0.5M KCl and Zcm3
of water to make up the fertilizer solution.

Determine X, Y and Z for Alvin.

更新1:

typing mistaken: He is given a bottle of 0.5M NH4NO3 and a bottle of 0.5M KCl.

回答 (1)

Uncle Michael

2008-04-13 6:02 am

✔ 最佳答案

N is provided by NH4NO3.
No. of moles of NH4NO3 = MV = 0.5 x (X/1000) = 0.0005X mol
Each mole of NH4NO3 contains 2 moles of N atoms.
No. of moles of N atoms = (0.0005X) x 2 = 0.001X mol
Molar mass of N atoms = 14 g mol-1
Mass of N = mol x (molar mass) = (0.001X) x 14 = 0.014X g = 2 g
Hence X = 2/0.014 = 142.9

K is provided by KCl.
No. of moles of KCl = MV = 0.5 x (Y/1000) = 0.0005Y mol
Each mole of KCl contains 1 mole of K atoms (actually, K+ ions).
No. of moles of K atoms = 0.0005Y mol
Molar mass of K atoms = 39 g mol-1
Mass of K = mol x (molar mass) = (0.0005Y) x 39 = 0.0195Y g = 1 g
Hence Y = 1/0.0195 = 51.3

Consider the total volume.
X + Y + Z = 250
142.9 + 51.3 + Z = 250
Hence, Z = 55.8

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