Unit 1-MOLE

[ben_ess12]

I no all of you would be busy studying for your midyear and goodluck as well!! but i need some guidance in how to go about these questions....

Calculate the mass of TNT that contains 12x10^23 carbon atoms

TNT= C7H5N3O6

Calculate the amount (mol) of O2 molecules contained in 0.2 mol of TNT

Any help would be greatly appreciated

[moekamo]

first one:



we divide by 7 since there are 7 C's per TNT molecule. the 227 is the molar mass of TNT, then mass=mols x molar mass

i got 64.62g for the answer

second one:

well in 0.2 mol TNT you would have 6 times the amount of O since its O6, so then youd have 3 times the amount of O2,
i.e

EDIT: fixed mistake in the second one...

[RobM8]

second one:

well in 0.2 mol TNT you would have 1/6th the amount of O since its O6, so then youd have 1/3rd the amount of O2,
i.e

In 10 molecules of H2O there are 10 O's and 20 H's. n(H2) = 3 x n(H6) = 1/2 x n(H)

back to the question:
In every O6 there are 3 O2's. [ meaning that 3 x n(O6) = n(O2) ]
In 0.2 mol of TNT there is 0.2 mol of O6
Hence there is 0.6 mol of O2.

calculations:
n(O6) = 0.2
n(O3) = 3 x 0.2 = 0.6 mol

[schnappy]

There are no oxygen molecules in TNT, TNT is detonated and it releases oxygen molecules.

[moekamo]

second one:

well in 0.2 mol TNT you would have 1/6th the amount of O since its O6, so then youd have 1/3rd the amount of O2,
i.e

In 10 molecules of H2O there are 10 O's and 20 H's. n(H2) = 3 x n(H6) = 1/2 x n(H2)

back to the question:
In every O6 there are 3 O2's. [ meaning that 3 x n(O6) = n(O2) ]
In 0.2 mol of TNT there is 0.2 mol of O6
Hence there is 0.6 mol of O2.

calculations:
n(O6) = 0.2
n(O3) = 3 x 0.2 = 0.6 mol

duuh yea oops :S ill fix that up now...