Answer:
1.15 M
Explanation:
Step 1: Given data
- Initial volume (V₁): 0.125 L
- Initial concentration (C₁): 3.00 M
- Final volume (V₂): 0.325 L
- Final concentration (C₂): ?
Step 2: Calculate the final concentration of the solution
We want to prepare a dilute solution from a concentrated one by adding water. We can calculate the concentration of the dilute solution using the dilution rule.
C₁ × V₁ = C₂ × V₂
C₂ = C₁ × V₁/V₂
C₂ = 3.00 M × 0.125 L/0.325 L = 1.15 M
To answer this question, you need to know the concept of half-life, which is how a radioactive material decreases in mass over time.
The half life of U-235 is 703.8 million years. The first part of this problem is to find the scale factor. To do this, divide the time that has past by the half life, like this:

Now, take this scale factor and multiply it by the current mass, like this:

This number is what you add to the current mass to get the original mass. That is because the scale factor showed us that it was just over one half life. Since after one half life, the mass is cut in half, and this is over one half life, when we add to the original it will be a little over double. This equation illustrates the final addition:

I hope this helped you. Fell free to ask any further questions.
Answer:
449 (g K) / 39.1 (g/mol K) = 11.5 mol K
Explanation:
Potassium has atomic number 39.1
amount of K in 449g sample = 449/39.1 = 11.5 mol