an aquarium must contain 3.6g of NaCl per 100g of H20.what is the percent by mass of the NaCl in the solution?
Answers
Answer:
In our example, the first dissolved compound is NaCl; the mass percent is (10 g / 136 g) x 100 percent = 7.35 percent. Divide the mass of the second dissolved component by mass of the solution followed by multiplying by 100 to calculate the mass percentage.
Explanation:
Answer:
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100mL solution of NaCl in water used 2.9g of salt. The final concentration is 0.50 M. express the concentration as a mass/volume %. How do these values compare to the molarity? Why? Show all calculations
mass/volume % formula is
mass of solute (g) / mass of solvent (mL)
Chemistry Molarity
1 Answer
Stefan V.
Dec 11, 2016
% m/v = 2.9% NaCl
Explanation:
A solution's mass by volume percent concentration,
% m/v
, is determined by looking at the number of grams of solute present in
100 mL
of solution.
In your case,
2.9 g
of sodium chloride, your solute, present in
100 mL
of solution would give you a
2.9% m/v
solution.
100
mL solution
⋅
given by the problem
2.9 g NaCl
100
mL solution
=
2.9 g NaCl
Therefore, you have
% m/v
=
2.9% NaCl
−−−−−−−−−−−−−−−−−−−−−
As you know, the number of moles of solute is calculated by dividing its mass by its molar mass. In this case, sodium chloride has a molar mass of
58.44 g mol
−
1
, which means that you have
2.9
g
⋅
1 mole NaCl
58.44
g
≈
0.050 moles NaCl
Now, molarity,
c
, is calculated by taking into account the number of moles of solute present in
1 L
of solution, so
1
L solution
⋅
10
3
mL
1
L
⋅
0.050 moles NaCl
100
mL solution
=
0.50 M
−−−−−−
As you can see, the mass by volume percent concentration has a higher value than the solution's molarity.
Now, in order to get from molarity to mass by volume percent concentration, you must
divide the molarity by 10
−−−−−−−−−−−−−−−−−−−−−−
This ensures that you're working with the number of moles of solute present in
100 mL
of solution
multiply the result by the molar mass of the solute
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
This ensures that you;'re working with the number of grams of solute present in
100 mL
of solution
So, let's try this out using a
1.5-M
solution of sodium chloride. You will have
1.5
10
=
0.15
→
the number of moles of solute present in
100 mL
of solution
0.15
⋅
58.44
≈
8.8
→
the number of grams of solute present in
100 mL
of solution
Therefore, you can say that
% m/v = 8.8% NaCl
−−−−−−−−−−−−−−−−−−
and
c
NaCl
=
1.5 M
−−−−−−−−−−−−
Answer link
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Molarity
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