The concentration of the stock solution will be approximately 7.50 x 10-5 M. How many milliliters of this stock solution is needed to prepare 50.0 mL of a 1.20 x 10-5 M solution? (Express your answer in the correct number of significant figures.
You want to dilute it 7.50/1.20 times (6.25 times). That means one part original, and 5.25 parts water. What is one part? 50ml/6.25= 8 ml of stock solution. Check significant figures.
To determine the volume of the stock solution needed, we can use the dilution equation:
C1V1 = C2V2
where C1 is the concentration of the stock solution, V1 is the volume of the stock solution needed, C2 is the concentration of the final solution, and V2 is the final volume of the diluted solution.
Given information:
C1 = 7.50 x 10^(-5) M
C2 = 1.20 x 10^(-5) M
V2 = 50.0 mL
Rearranging the equation, we can solve for V1:
V1 = (C2 * V2) / C1
Plugging in the values:
V1 = (1.20 x 10^(-5) M * 50.0 mL) / 7.50 x 10^(-5) M
V1 = (6.00 x 10^(-4) mL * mL) / 7.50
V1 = 0.0000800 mL
To express the answer in the correct number of significant figures, we need to consider the given values. The concentration of the stock solution (C1) has three significant figures, and the final volume of the diluted solution (V2) also has three significant figures. Therefore, the answer should be expressed with three significant figures:
V1 ≈ 0.0000800 mL
However, it is important to note that this answer is smaller than one milliliter (mL) and can be better expressed in a different unit, such as microliters (μL). There are 1000 μL in one mL:
V1 ≈ 80.0 μL.