The Student Room Group

2 mole questions

1. What amount of solute ions, in moles, is present in 50 cm3 of 0.10 mol dm–3 sodium hydroxide solution?

I thought 0.05 * 0.1? But thats wrong

2. A blast furnace contains 1600 kg of iron(III) oxide (Mr=160) and 144 kg of carbon (Ar=12). Assuming that they react according to the following equation:
Fe2O3+3C2Fe+3COFe_2O_3 + 3C \to 2Fe + 3CO; what is the limiting reagent and the maximum theoretical yield of iron?

I said Iron limits and 1200 kg of Fe products, but thats wrong
1. Moles = conc. * volume.
You need to convert the volume so its relative to the concentration first. 50 / 1000 = 0.05dm3. 0.10 mol dm-3 * 0.05dm3 = 0.005moles of sodium hydroxide.
However in aqueous solution NaOH will dissociate to form Na+ and OH- - two seperate species, of which you have 0.005moles of each.
So the answer is 0.005 + 0.005.

Remember if you started with ONE molecule of NaOH, this will become TWO ions. So the number of moles will double.

Latest