Question

A sample of quick lime weights 400 mg. If 2*10^21 atoms are removed from the sample, calculate the number of molecules left is the sample




Please solve this is very urgent ^_^

Answer 1

Total number of molecules = number of moles * Avogadro's number (6.02*10^23)

Since number of moles is unknown, so we have to calculate that first

Number of moles = Mass÷ molecular mass ( mass of one mole )

The molecular mass of quick lime is 56 ( 16 for oxygen and 40 for calcium)

= 0.4 (mass in gram)÷ 56 = 0.0071

So total number of molecules is 0.0071*6.02*10^23

Molecules left = previous answer - (2*10^21 deviding this number by 2 since each molecule consists of 2 atoms)

= Your answer

Good luck.