Answer:
Explanation:
Here we want to find the largest area of a circle that can be made from a piece of thread 25.2 cm long, assume no knot .
This means that the circumference of the circle must equal to the length of the thread, so we can write:
L = 25.2 cm
And the circumference can be written as:
where
r is the radius of the circle
Solving for r, we find the radius:
The area of a circle is given by the formula
So in this case, we find:
Answer:
Here's what I get
Explanation:
You want to dilute the original solution by a factor of 25 in two steps, so you could dilute it by a factor of 5 in the first step, then dilute the new solution by another factor of 5.
A. First dilution
Use a 10 mL pipet to transfer 10 mL of the original solution to a 50 mL volumetric flask. Make up to the mark with distilled water. Shake well to mix.
Use the dilution formula to calculate the new concentration.
B. Second dilution
Repeat Step 1, using the 0.003 970 mol·L⁻¹ solution.
3. Check:
Compare the final concentration with the original