What mass will remain. Please help me. So hard. ?

Question

At noon on Monday, you measure the mass of a sample of 183/76 Os and find the mass is 802 g. What mass of 183/76 Os will remain at noon on the following Monday?

Answer 1

To answer this question, you need to know the Half-life of Osmium-183.  Assuming it's not written in your book somewhere, you could look it up online.

Half-life of Osmium= .544 days.

Time passed= 7 days(exact number)

Since 7 days passed and .544 days is the half life of Osmium-183

7 days/.544 days or approx. 12.9 half-lives have passed.

Now you have to multiply the mass of Osmium-183 at the beginning of the first week by 1/2... 12.9 times.

So, 802 g. x (1/2)^12.9 = .105 g.

That should be your answer, unless I've completely confused this with something else... In which case... Sorry.