Chemistry Concentration and Molarity Lab

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Determining the Concentration of an Unknown Solution
Graph: The effect of concentration of CuS04 * 5H20 on transmittance.

I solved for my unknown by plugging in “y” as my given transmittance value, which was 85.0. y = -278x + 100.12
.85 = -278x + 100.12
-99.27 = -278x
X = .357M (concentration)

The relationship between the transmittance values and the concentration is an indirect relationship. Whenever the concentration increases, the transmittance decreases. It can also be reversed, so when the concentration decreases, the transmittance increases. For this graph, the line should not touch the origin because it is a negative slope. In order for the concentration to be 0, the transmittance level must be at exactly 100%. This means that all the light particles are transmitted directly through the object without any levels of concentration.

Y = 1.4599x – 0.0068
.07 = 1.4559x – 0.0068
X = 0.05

The 2nd graph was between concentration and absorbance. This is a direct relationship because as the concentration increased, the absorbance also increased. For this graph, the line should touch the origin because it is a positive slope going from lower values to higher values. Also it passes through the origin because direct variation relationships are in the form of y = mx, where y and m are constant variables. For the absorbance value to zero, the concentration must be also be zero.

Should the line of Concentration versus Absorbance go through the origin? As stated above, the line should touch and go through the origin eventually because it is a positive slope going from lower values to higher values. It is a direct variation relationship. Concentration (M)| Transmittance %| Absorbance|

.02M| 94.8%| 0.02|
.04M| 88.6%| 0.05|
.06M| 83.0%| 0.08|
.08M| 79.0%| 0.10|
.10M| 71.8%| 0.14|
.357M | 85.0% | 0.05 |
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