1 What is the concentration of hydrogen ions in 0.05mol/dm3 sulfuric acid?
I will present you my working. Not sure if I'm right, but please point out the error.
H2SO4 ----> 2H+ + SO4 2-
Assuming that volume of acid is 1 dm3,
No. of mols of H2SO4 = concentration X vol
= 0.05 X 1
= 0.05 mols
Comparing mole ratio, we know that no. of moles of H+ ions is 0.10 mol
so concentration is 0.10 mol/dm3
concentration in mol/dm3 = concentration of g/dm3 / relative Mr of substance
concentration of H+ ions (in g/dm3) = 0.10 mol/dm3 X 1
= 0.10 g/dm3 (final answer) - please verify
the answer is correct, but not sure if my working is correct or not.
I multiply by 1 since Ar of hydrogen is 1.
2. Propane burns completely in oxygen according to the equation shown
C3H8 + 5O2 ----> 3CO2 + 4H2O
If 0.1 mol of propane gas is burnt completely, which volume of gaseous product is obtained, measured at r.t.p?
A 0.1 dm3 B 0.3dm3 C 2.4 dm3 D 7.2 dm3
My answer is D. TYS answer is A. I compared the mole ratio of propane to CO2 gas, so we have 0.3 mol of CO2 being produced. 0.3 X 24 dm3 = 7.2dm3
3. This is the part where I need serious help. Can't do this question at all.
Which ion is present in the highest concentration in a 2mol/dm3 aqueous solution of sodium sulfate?
The choices are hydrogen ions, hydroxide ions, sodium ions, and sulfate ions.
4 All ammonium salts on heating with NaOH produce NH3 gas. From which ammonium salt can the greatest mass of ammonia be obtained?
0.5 mol (NH4)3PO4
0.5 mol (NH4)2SO4
1.0 mol NH4Cl
1.0 mol NH4NO3
Don't really know how to go about calculating this.
lastly, which fertilizer provides the most nitrogen per mole?
NH4NO3 OR (NH4)3PO4 OR NaNO3 OR (NH4)2SO4
If I calculate using %tage composition, my answer would be NH4NO3. If I simply look at the no. of Nitrogen atoms from the formula given, my answer is (NH4)3PO4. Answer is (NH4)3PO4. I think they look at the no. of nitrogen atoms. Is this method accepted?
*****Alas, the MOST IMPORTANT questions are 3 and 4 cuz I have totally no clue how to sovle them... the rest, i merely need you guys to check my working. *****
Thanks
For qn 4, always just look at the compound. NH3 comes from the NH4 so look for the compound with the most amount of N in their NH4 which makes the 1st answer having the most N being 1.5moles while the other 3 are all 1 mole each.
For the fertiliser qn, its just the number of N atoms.
Originally posted by bonkysleuth:1 What is the concentration of hydrogen ions in 0.05mol/dm3 sulfuric acid?
I will present you my working. Not sure if I'm right, but please point out the error.
H2SO4 ----> 2H+ + SO4 2-
Assuming that volume of acid is 1 dm3,
No. of mols of H2SO4 = concentration X vol
= 0.05 X 1
= 0.05 mols
Comparing mole ratio, we know that no. of moles of H+ ions is 0.10 mol
so concentration is 0.10 mol/dm3
concentration in mol/dm3 = concentration of g/dm3 / relative Mr of substance
concentration of H+ ions (in g/dm3) = 0.10 mol/dm3 X 1
= 0.10 g/dm3 (final answer) - please verify
the answer is correct, but not sure if my working is correct or not.
I multiply by 1 since Ar of hydrogen is 1.
2. Propane burns completely in oxygen according to the equation shown
C3H8 + 5O2 ----> 3CO2 + 4H2O
If 0.1 mol of propane gas is burnt completely, which volume of gaseous product is obtained, measured at r.t.p?
A 0.1 dm3 B 0.3dm3 C 2.4 dm3 D 7.2 dm3
My answer is D. TYS answer is A. I compared the mole ratio of propane to CO2 gas, so we have 0.3 mol of CO2 being produced. 0.3 X 24 dm3 = 7.2dm3
3. This is the part where I need serious help. Can't do this question at all.
Which ion is present in the highest concentration in a 2mol/dm3 aqueous solution of sodium sulfate?
The choices are hydrogen ions, hydroxide ions, sodium ions, and sulfate ions.
4 All ammonium salts on heating with NaOH produce NH3 gas. From which ammonium salt can the greatest mass of ammonia be obtained?
0.5 mol (NH4)3PO4
0.5 mol (NH4)2SO4
1.0 mol NH4Cl
1.0 mol NH4NO3
Don't really know how to go about calculating this.
lastly, which fertilizer provides the most nitrogen per mole?
NH4NO3 OR (NH4)3PO4 OR NaNO3 OR (NH4)2SO4
If I calculate using %tage composition, my answer would be NH4NO3. If I simply look at the no. of Nitrogen atoms from the formula given, my answer is (NH4)3PO4. Answer is (NH4)3PO4. I think they look at the no. of nitrogen atoms. Is this method accepted?
*****Alas, the MOST IMPORTANT questions are 3 and 4 cuz I have totally no clue how to sovle them... the rest, i merely need you guys to check my working. *****
Thanks
Hi Bonkysleuth,
Do have a look at JM's post for a solution for question 3.
http://www.simplechemconcepts.com/o-levels-chemistry-questions-mole-concepts-mole-calculations/
Cheers.
geez.
Which ion is present in the highest concentration in a 2mol/dm3 aqueous solution of sodium sulfate?
The choices are hydrogen ions, hydroxide ions, sodium ions, and sulfate ions.
compound : Na2SO4
highest should be sodium ion . because got 2 .
i doubt u will understand. perhaps im wrong. =)
2) my ans is D also
1) 0.05 x2 = 0.1 ( ans)
4) A . look at nh3.