Question

One uranium atom has a mass of 3.95 x 10^-22 grams.

a) work out an estimate for the number of uranium atoms in 1kg
b) is your answer to (a) an underestimate or an overestimate?
Give reason for your answer.

Please help! Thanks.

Answer 1

remember
(ab)/(cd)=(a/c)(b/d)
and

`(x^n)/(x^m)=x^(n-m)`

1kg=1000g=1*10^3g
hmm, I estimate, 4 of them

x=number of attoms
mass of 1 times x=1*10^3
3.95*10^-22 times x=1*10^3
divide both sides by 3.95*10^-22
x=
`(1*10^3)/(3.95*10^(-22))= ((1)/(3.95) )( (10^(3))/(10^(-22)) )`=
`0.25316*10^(25)`=
`2.5316*10^(24)`
a million has 9 zeroes
so 24 zeroes is alot that is a septillion, so there are 2.5316 septillion uranium atoms in 1kg


a. 4
b. underestimate