Compute/answer the problem 1 and 2. Write your answer in a clean paper. Take a picture of your computation and upload it in our GCR. 1. Dissolve 15 grams of Sugar in 150 grams of water. Compute for the concentration by mass. 2. Determine the percent by volume of solution made by combining 20 mL of methanol with enough water to produce 180 mL of the solution.
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Verified answer
Percent Concentration
1. Given:
mass of sugar (solute) = 15 g sugar
mass of water (solvent) = 150 g water
Solution:
Concentration by mass =
x 100%
=
x 100%
=
x 100%
=
x 100%
= (0.0909091) x 100%
= 9.09%
There are 9.09% of sugar in the solution
2. Given:
volume of solute (methanol) = 20 mL
volume of solution (methanol + water)= 180 mL
Solution:
% volume =
x 100%
=
x 100%
= 0.1111 x 100%
= 11.11%
There are 11.11% of methanol in the solution.
Explanation:
Mass Concentration
There are several ways of expressing the concentration of a solution by using a percentage. One of which is the mass/mass percent (% m/m). This is defined as the mass of a solute divided by the mass of a solution and multiplied by 100:
Concentration by mass =
x 100%
It is important to note that the mass of a solution is the sum of the mass of solute and solvent. In the given problem, there is no total mass of the solution thus, we add the mass of solute and solvent. Also, in computing, each mass must be expressed in the same units to determine the proper concentration.
Volume percent
The volume percent of a solution is another way to determine the concentration. It is the ratio of the volume of solute that is present in a solution, as compared to the volume of the solution, as a whole. Additionally, because this type of concentration, which is typically calculated for liquid- and gas-phase solutions, is expressed as a percentage, this proportion must be multiplied by 100 as shown below:
Volume Percent =
× 100 %
We have also to make sure that the units are the same to solve for % volume.
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