Isolate the lab immediately mercury can be easily tracked throughout a lab by people walking on spill. laboratory staff can safely clean up small spill . don't stamp on small pieces . carefully inspect the bench tops and floors before sitting. to avoid hurting .
16 atoms of hydrogen and 8 atoms of oxygen
It seems that you have missed the necessary options for us to answer this question, but anyway here is the answer. William adds two values, following the rules for using significant figures in computations. He should write the sum of these two numbers by using the same number of decimal places as the least precise value. Hope this helps.
Molecular weight of vanillin = 152 g/mol
Futher molecular formula of vanillin is C8H8O3
Atomic weight of oxygen = 16 g/mol
Thus, 152 g of vanillin contains 16 g of oxygen
∴ 0.045 g (45 mg) of vanillin contains

= 0.00473 g
Also, number of moles of vanillin in 0.045 g sample =

Now, 1 mole = 6.023 X 10^23 molecules
∴ 2.96 X 10^-4 mole = 1.78 X 10^20 molecules
From molecular formula, it can be seen that 1 molecule of vanallin contain 3 atoms of oxygen
∴1.78 X 10^20 molecules contain 3 X 1.78 X 10^20 = 5.34 X 10^20 oxygen atoms
That the surface is very shiny