Chemistry exam question help needed (1 Viewer)

wiliaamnguuyen · Aug 15, 2015

Question is: Aluminium oxide can decomposed by electrolysis. If 5kg of aluminium oxide yields 2.65kg of aluminium on electrolysis. Calculate the percentage composition of aluminium oxide.

MilkyCat_ · Aug 16, 2015

Since you are already given the mass of aluminium you don't have to use the empirical formula to determine the percent composition by mass

For aluminium 2.65/5= 0.53
therefore 53% aluminium
For oxygen (5-2.65)/5= 0.47
therefore 47% oxygen

DatAtarLyfe · Aug 16, 2015

Oh shit, milfy cookin up dat chemistry shit

wiliaamnguuyen · Aug 16, 2015

Does helium atom have the same electronic configuration as hydrogen atom??

wiliaamnguuyen · Aug 16, 2015

Oh can you also help me with this exam question? There's no solutions, and I have to check to make sure if someone has got the same as I did
(16) A student completely reacted some solid iron (II) sulfide in 200mL of 0.5M hydrochloric acid, forming iron (II) chloride in solution and collecting all the hydrogen sulphide gas produced. The volume of the hydrogen was 122.5mL at room temperature (25 degrees celsius) and pressure (100kPa).
(a) Calculate the number of moles of hydrogen sulfide gas collected
(b) Determine the mass of iron (II) sulfide used in the experiment
(c) Using a calculation, show that the amount of hydrochloric acid used was in excess

wiliaamnguuyen · Aug 18, 2015

Anyone can help?

InteGrand · Aug 18, 2015

wiliaamnguuyen said:
Does helium atom have the same electronic configuration as hydrogen atom??

No. Hydrogen has one electron, Helium has two.

rand_althor · Aug 18, 2015

wiliaamnguuyen said:
Oh can you also help me with this exam question? There's no solutions, and I have to check to make sure if someone has got the same as I did
(16) A student completely reacted some solid iron (II) sulfide in 200mL of 0.5M hydrochloric acid, forming iron (II) chloride in solution and collecting all the hydrogen sulphide gas produced. The volume of the hydrogen was 122.5mL at room temperature (25 degrees celsius) and pressure (100kPa).
(a) Calculate the number of moles of hydrogen sulfide gas collected
(b) Determine the mass of iron (II) sulfide used in the experiment
(c) Using a calculation, show that the amount of hydrochloric acid used was in excess

$The reaction is: FeS$_{(s)}$ + 2HCl$_{(aq)}$ $\to$ FeCl$_{2}$ + H$_{2}$S$_{(g)}$.$

$$(a) n(H$_2$S) $=\frac{V}{V_m}=\frac{0.1225}{24.79}=0.00494$ moles.$

$$(b) n(FeS) $=$ n(H$_{2}$S)$=0.00494$ moles. \\m(FeS) $=n \times M =0.00494 \times [55.85+32.07]=0.43446 $ grams.$

$$(c) n(Reacted HCl) $=$ 2n(FeS) $=0.00988$ moles. \\ n(Total HCl) $=c \times V=0.2 \times 0.5=0.1$ moles. \\ n(Excess HCl) $=$ n(Total HCl) $-$ n(Reacted HCl) $=0.1-0.00988=0.09012$ moles. Therefore the amount of HCl used was in excess.$

Chemistry exam question help needed (1 Viewer)

wiliaamnguuyen

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