Concentration of Solutions
Concentration of Solutions
Concentration of Solutions
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Name Class Date<br />
Problem Solving continued<br />
Sample Problem 1<br />
What is the percentage by mass <strong>of</strong> a solution made by dissolving 0.49 g <strong>of</strong><br />
potassium sulfate in 12.70 g <strong>of</strong> water?<br />
Solution<br />
ANALYZE<br />
What is given in the problem?<br />
What are you asked to find?<br />
the mass <strong>of</strong> solvent, and the mass <strong>of</strong> solute,<br />
K 2 SO 4<br />
the concentration <strong>of</strong> the solution expressed as<br />
a percentage by mass<br />
Items<br />
Mass <strong>of</strong> solvent<br />
Data<br />
12.70 g H 2 O<br />
PLAN<br />
What step is needed to calculate the concentration <strong>of</strong> the solution as a percentage<br />
by mass?<br />
Divide the mass <strong>of</strong> solute by the mass <strong>of</strong> the solution and multiply by 100.<br />
1<br />
Mass <strong>of</strong> water in g <br />
Mass <strong>of</strong> solute 0.49 g K 2 SO 4<br />
<strong>Concentration</strong> (% by mass) ? %<br />
2<br />
Mass <strong>of</strong> K 2<br />
SO 4<br />
in g<br />
<br />
3<br />
Mass <strong>of</strong> K 2<br />
SO 4<br />
solution in g<br />
percentage solute mass<br />
concentration<br />
100<br />
solution mass<br />
4<br />
Percentage<br />
K 2<br />
SO 4<br />
by mass<br />
given<br />
g K 2<br />
SO 4 100<br />
percentage concentration g K2 SO 4<br />
g H 2<br />
O<br />
given<br />
given<br />
COMPUTE<br />
0.49 g K<br />
percentage concentration 2 SO<br />
4<br />
100 3.7% K 2 SO 4<br />
0.49 g K 2 SO 4 12.70 g H 2 O<br />
EVALUATE<br />
Are the units correct?<br />
Yes; percentage K 2 SO 4 was required.<br />
Is the number <strong>of</strong> significant figures correct?<br />
Yes; the number <strong>of</strong> significant figures is correct because the data had a minimum<br />
<strong>of</strong> two significant figures.<br />
Copyright © by Holt, Rinehart and Winston. All rights reserved.<br />
Holt ChemFile: Problem-Solving Workbook 198 <strong>Concentration</strong> <strong>of</strong> <strong>Solutions</strong>
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