Chemistry Moles Questions, Need Help

1) When 1.17g of potassium is heated in oxygen 2.13g of an oxide are produced. In the case of this oxide the empirical and molecular formulae are the same. What is the molecular formula of the oxide produced?

2)A solution of copper sulphate reacts with sodium hydroxide solution to produce a precipitate of copper hydroxide according to the following equation

CuSO^4(aq) + 2NaOH(aq) -> Cu(OH)^2(s) + Na^2SO^4

What mass of sodium hydroxide would be needed to convert 15.95g of copper sulphate to copper hydroxide and what mass of copper hydroxide would be produced?

3) When 13.9g of FeSo^4.xH20 are heated 4g of solid iron(III) oxide are produced together with the loss of 1.6g of sulphur dioxide and 2.0g of Sulphur Trioxide. The rest of the mass loss being due to the warer of crystallization being lost. Use the data to write the full equation for the action of heat.

4) When an oxide of carbon containing 57.1% oxygen is burnt in the air the percentage of oxygen joined to the carbon increases to 72.7%. Show that this data is consistent with the combustion of carbon monoxide to carbon dioxide.

Please help me out, Im in deep crap!

Reply 1

Misogynist

Someone help me out here!!!

Reply 2

Misogynist

Why isnt someone helping me? :confused:

Reply 3

BCHL85

Godsize

number of moles of K = 1.17/39 = 0.03 mole
Mass of oxygen reacted = 2.13 - 1.17 = 0.96g
Number of moles of O2 = 0.96/32 = 0.03 mole
nK : nO2 = 1:1, so the reaction equation is:
K + O2 = KO2.
The oxide produced is KO2

2)A solution of copper sulphate reacts with sodium hydroxide solution to produce a precipitate of copper hydroxide according to the following equation

CuSO^4(aq) + 2NaOH(aq) -> Cu(OH)^2(s) + Na^2SO^4

What mass of sodium hydroxide would be needed to convert 15.95g of copper sulphate to copper hydroxide and what mass of copper hydroxide would be produced?

Number of moles of CuSO4 = 15.95/159.5 = 0.01 mole (M(Cu) = 63.5)
According to the equation
-number of moles of NaOH needed = 2*0.01 = 0.02 mole.
-number of moles of Cu(OH)2 = 0.01 mole
Mass of NaOH = 0.02* 40 = 0.8g
Mass of Cu(OH)2 = 0.01*97.5 = 0.975g.

3) When 13.9g of FeSo^4.xH20 are heated 4g of solid iron(III) oxide are produced together with the loss of 1.6g of sulphur dioxide and 2.0g of Sulphur Trioxide. The rest of the mass loss being due to the warer of crystallization being lost. Use the data to write the full equation for the action of heat.

Mass of H20 lost = 13.9 - (4 + 1.6 + 2) =6.3 g
Number of moles of
- Fe2O3 = 4/160 = 0.025 mole
- SO2 = 1.6/64 = 0.025 mole
- SO3 = 2.0/80 = 0.025 mole
- H20 = 6.3/18 = 0.35 mole
- FeSO4 (in FeSO4.xH2O) = number of moles of Fe = 2*that of Fe2O3 = 2*0.025 = 0.05 mole
So nH2O/nFeSO4 = x/1 , then 0.35/0.05 = x, so x = 7.
nFe2O3 : nSO2 : nSO3 = 1 : 1 : 1
The equation should be:
2FeSO4.7H2O ---> Fe2O3 + SO2 + SO3 + 14H2O.

4) When an oxide of carbon containing 57.1% oxygen is burnt in the air the percentage of oxygen joined to the carbon increases to 72.7%. Show that this data is consistent with the combustion of carbon monoxide to carbon dioxide.

The initial oxide of carbon

nO : nC = 57.1/16 : 42.9/12
         3.57     : 3.57
             1    : 1

The empirical formula: CO
The oxide of Carbon produced

 nO : nC = 72.7/16 : 27.3/12
              4.54 :  2.27
               2   : 1

The emprical formula: CO2
So we have
2CO + O2 --> 2CO2.

Please help me out, Im in deep crap!

It's not so hard like a deep crap dude :cool:

. Please try to solve before asking, ok? :tongue:

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