G-Chem questions

[2dds2009]

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Can you guys please help me out with those problems?

If a solution which is 0.50M in a compound X decomposes for 5.0 minutes at an average of 0.040M.min-1, the new concentration o X will be?

0.04
0.05
0.20
0.30
0.50

A 49 gram sample of sulfuric acid, H2S04 (98g.mol-1) contains

1 mol of S
26 grams of O
2.0 grams of H
2 moles of O atoms
1 mole of molecules

For this one, I tried to do: 49g/98g/moles to find 0.5 moles total. then I did 0.5/ 4 moles of oxygen to find 2 moles of O atoms. Is that the right way to find the answer?

Thanks .

 

[g3k]

Can you guys please help me out with those problems?

If a solution which is 0.50M in a compound X decomposes for 5.0 minutes at an average of 0.040M.min-1, the new concentration o X will be?

0.04
0.05
0.20
0.30
0.50

A 49 gram sample of sulfuric acid, H2S04 (98g.mol-1) contains

1 mol of S
26 grams of O
2.0 grams of H
2 moles of O atoms
1 mole of molecules

For this one, I tried to do: 49g/98g/moles to find 0.5 moles total. then I did 0.5/ 4 moles of oxygen to find 2 moles of O atoms. Is that the right way to find the answer?

Thanks .

1) In 1 minute, .04 moles decompose
In 5 minutes, .04moles/min x 5 minutes = .2moles have decomposed
Implies after 5 minutes, the no. of moles of X (in 1 liter) :
.5moles-.2moles=.3 moles
Concentration is .3M
2) I think what you did was correct.

Someone please do confirm my answers

 

[beannaithe]

A 49 gram sample of sulfuric acid, H2S04 (98g.mol-1) contains

1 mol of S
26 grams of O
2.0 grams of H
2 moles of O atoms
1 mole of molecules


g3k, you are right.

1- 0.3M is left..g3k did it the right way.

2 - the way i looked at it was that there is 1/2 mole of H2SO4. thus, there can't be 1 mole of S, 1 mole of molecules, or 2 grams of H. there also can't be 26g of O because in 1/2 mole of H2SO4 there would be, 32g. so the answer is 2 moles of O atoms.

the way you did it works too, was just giving you another way of looking at it...mind if i ask you where you go thte questions from? i remember it from somewhere, but i can't remember! 😀

good luck!