Answer:
4.44 M
Explanation:
The absorbance of a solution is a function of its concentration through the equation, known as Beer's law, as:
A = ε c l
where A is the absorbance, ε is is a constant of proportionality called molar absorptivity in units of L/mol·cm, c is the concentration in mol/L (M), and l is the length of the cuvette we use to measure the absorbance, usually 1 cm.
Now the above equation is a function of c in the form y= mx + b, which is exactly the linear relationship stated in the question.
Therefore
y = 0.0425 + 0.011
A = (εl) c
Therefore
slope = m = ε (1) = 0.0425
Knowing ε we can calculate the concentration of the diluted unknown:
0.200 = 0.0425 c + 0.011
c = (0.200 - 0.011)/0.425 = 0.44 M
This the concentration of the diluted solution, the original concentration of the unknown solution can be calculated from the formula V₁M₁ = V₂M₂
calling M₁ our undiluted solution, we have
M₁ = V₂M₂/V₁ = 50 mL x 0.44 M / 5.00mL = 4.44 M
(Notice there is no need to convert the volume to liters in the above equation since they appear in both sides of the equation and so they cancel each other).
