If 6.90 g of (half-life = 5.30 y) are allowed to decay, how many grams would be left after 1.00 y and after 10.0 y?

Answer 1

Calculate k.
k = 0.693/t(1/2)

Then put k into the following:
ln(No/N) = kt
No = 6.90 g
N = solve for that.

Answer 2

i did that! i got 7.86 but its wrong what di dyou get?

Answer 3

For the 1 yr it's about 6 g remaining.
For the 10 yr it's 2 g remaining.
Post your work and I'll find your error.