1. You need to make an aqueous solution of 0.241 M chromium(II) bromide for an e
ID: 891018 • Letter: 1
Question
1. You need to make an aqueous solution of 0.241 M chromium(II) bromide for an experiment in lab, using a 125 mL volumetric flask. How much solid chromium(II) bromide should you add? __________ g
2. How many milliliters of an aqueous solution of 0.146 M copper(II) sulfate is needed to obtain 16.9 grams of the salt? __________ mL
3. In the laboratory, a student dilutes 10.1 mL of a 7.18 M hydrobromic acid solution to a total volume of 250.0 mL. What is the concentration of the diluted solution ? ___________ M
Explanation / Answer
(1) CuBr2 molar mass = 223.35 g / mol
molarity CuBr2 = 0.241 M
volume (V) = 125 ml
molarity = (weight / molar mass ) x 1000 / volume (ml)
0.241 = ( weight / 223.35 ) x 1000 / 125
weight = 6.73 g
(2) CuSO4 molar mass = 159.6 g/mol
CuSo4 mass = 16.9 g
CuSO4 moles = mass / molar mass
= 16.9 / 159.6
= 0.106
molarity = (moles / volume ) x 1000
0.146 = (0.106 / V ) x 1000
V = 726 ml
volume = 726 ml
(3)
M1 V1 = M2 V2
7.18 x 10.1 = M2 x 250
M2 = 0.290 M
the concentration of the diluted solution =0.290 M
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