In the laboratory you are asked to make a 0.690 m chromium(II) nitrate solution

Question

In the laboratory you are asked to make a 0.690 m chromium(II) nitrate solution using 275 grams of water. How many grams of chromium(II) nitrate should you add?

An aqueous solution is made by dissolving 24.6 grams of barium bromide in 319 grams of water. The molality of barium bromide in the solution is_____

In the laboratory you are asked to make a 0.650 m sodium bromide solution using 12.6 grams of sodium bromide. How much water should you add in grams?

An aqueous solution of barium bromide has a concentration of 0.323 molal. The percent by mass of barium bromide in the solution is__________

Explanation / Answer

1) molality = w/mwt*1000/mass of solvent in grams

0.69 = (w/238.011)*(1000/275)

w = mass of chromium(II) nitrate must add = 45.16 grams

2) molalitry = (24.6/297.14)*(100/319) = 0.026 m

3) 0.65 = (12.6/102.894)*(1000/x)

x = mass of water required = 188.4 grams

4) 0.323 molal means, 0.323 mol barium bromide present in 1 kg solvent.

   mass of BaBr2 present in sample = 0.323*297.14 = 95.976 grams

mass of solution = 1000+95.976 = 1095.976 grams

% by mass = 95.976/1095.976*100 = 8.75%

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