5.9976 g of Na2CrO4 (MW = 161.97 g/mol) is dissolved in 1000.0 mL of water. Assu

Question

5.9976 g of Na2CrO4 (MW = 161.97 g/mol) is dissolved in 1000.0 mL of water. Assuming the solution has a density of 1.00 g/mL, what is the concentration of Na (MW = 22.9898 g/mol) in the solution in units of

5.9976 g of NazCrO4 (MW-161.97 g/mol) is dissolved in 1000.0 mL of water. Assuming the solution has a density of 1.00 g/mL, what is the concentration of Nat (MW 22.9898 g/mol) in the solution in units of a) molarity (M)? Number b) parts per thousand (ppt)? Number ppt c) 10.0 mL of the solution is then diluted to a final volume of 1000.0 mL. What is the concentration of Na* in the diluted solution in units of parts per million (ppm)? Number ppm

Explanation / Answer

5.9976/161.97 g/mol = 0.0370 moles

0.0370 moles has 0.037 x 2 = 0.074 moles of sodium

When it is dissolved in 1000 mL water the total weight is 1005.9976 g

So 0.074 moles in 1005.9976 g or 1005.9976 mL of solution as density is 1g/mL

so concentration is 0.074/1.005997 = 0.0736 M in Na+

0.0736 moles is 0.0736 x 22.98=1.69 g of sodium in 1005.997 g

so 1000 x 1.69/1006.997 = 1.68 ppt

c) N1V1=N2V2

1.68 x 10 = N2 x 1000

N2 = 0.0168 ppt which is 16.81 ppm

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