A)i need to find how many atoms of K there in 106 gr K3PO4

B)i need to calculation how many gr CH4 and how many mol S8 are necessary to react to get 0.002 mol of H2S (gas) in this reaction: 4CH4+2S8---->4CS2+8H2S


In b I have to find first the mM?

Thanks for help.

a)
Find the mM of K3PO4
Find how many mol of K3PO4 is 106 g of K3PO4
In 1 mol of K3PO4, there are 3 mol of K atoms. Find the number of moles of K there is in your sample of 106 g.
1 mol = 6.02x10^23 atoms. Find the number of atoms from the number of moles of K.

b) Notice that you can simplify your equation:

2CH4+S8---->2CS2+4H2S

The mole ratio is 2:1:4 when taking CH4:S8:H2S.

You have 0.002 mol H2S. Which mean you have how many moles of CH4 and S8?

Work out the mM of CH4 and S8 now, and with the number of moles, you should get the mass of CH4 and S8 required.

my answer for A) . Mm = 212 gr/mol
n = m/Mm = 106/212 = 0.5 mol
N = nx6.02x1023 = 0.5x6.02x1023 = 3.01x1023(K3PO4)
N = 3.01x1023x3 = 9.03x1023(K

B)i need 0.0005 of 2S8(s) and m(CH4) = nxMm = 0.001x16 = 0.016 gr

thank you as always.

Yes, that's it :)

Thank you.
By the way tomorrow I have the main exam so this why I try to do all the calculation question :)
Thank you.

No problem, we'd be glad to help :)