[spitkin]

Hi,
if anyone is there at the moment can you please help me with a few problems?

1. how many moles of H+ (Aq) ions are present in 750ml of .65M of Hydrochloric acid?

2. How many moles of oxygen are there in 34.81 g of CO2?

Thanks in advance

Sigrid

[Borek]

Please read forum rules. Show us what you know.

I don't like 2^nd question. Moles of what - O? O₂?

[chienbinhnam2324]

1 . HCl --> H+ + Cl-
    0.65     0.65        M
We get n(H+) = CV = 0.65*0.75 = 0.49 mol
2 . there are 34.81/44 moles of CO2
We can see that one mole of CO2 contain 2 moles of O
So there are 2*34.81/44 moles of O

Is it right

[spitkin]

2nd question, moles of O

1st question have tried to use the formula:  number of moles = mass (g) X (1 mol / no. of grams) but i cant get the correct answer. Am i using the correct formula?

[spitkin]

You are on fire. First one, cant believe how simple that was, sometime you jut need a different way of explaining it. I realised what i did wrong on the second one. I forgot to times it by 2 for O2. silly mistake
I have a couple more if you arent busy:

3. What mass of sodium nitrate must be dissolved in water to prepare 750ml of .640M of NaNO3 soloution?

4. If Hg and 2.20g of O2 are obtained from heating 77.0g HgO, whatis the mass percent yeild of O2? the hint is to try to work out the stoichiometry of the reaction first

5. Ammonia reacts with diatomic oxygen to form nitric oxide and water vapour, according to the following reaction
4NH3 + 5O2 --> 4NO + 6H2O
when 40g NH3 and 50g O2 are allowed to react, whats the limiting reagent?

last one i promise

6. What volume of .18M HCL soloution would be required to prepare 850ml of .00810M HCL soloution?

thanks for your help

[Borek]

Try and show what you did. These are not much harder then first two.