If the density of the solution is 1.50g/ml, calculate the concentration of the solution?

and also this question.. i tried it but I just don't get it..

Fe2O3(s)+3CO(g) ---> 2Fe(l) + 3O2(g)

Suppose that exactly 2 mol of iron iron(iii)oxide and 1 mol of carbon monoxide are mixed together and allowed to react in a furnace. After the reaction is complete, there are 0.667 mol of iron metal in the furnace. Is there an iron (iii) oxide or carbon monoxide left over unreacted in the flask after the reaction is complete? If so, which is left over and how much is left?

Help appreciated!

## Answers (1)

So 1 kg of the solution will contain 500 g HBr and 500 g H2O. Now, the 500 g HBr is:

500 g / 80.9 g/mol = 6.18 moles of HBr

The volume of the solution is: 1000 g / 1.50 g/mL = 667 mL = 0.667 L

So, the molar concentration of HBr in the solution is: 6.18 mol / 0.667 L = 9.27 M

This is a limiting reactant problem. Beginning with the Fe2O3, you could produce:

2 mol Fe2O3 X (2 mol Fe / 1 mol Fe2O3) = 4 mol Fe

Beginning the the CO, you could produce:

1 mol CO X (2 mol Fe / 3 mol CO) = 0.667 mol Fe

So, CO is the limiting reactant and it is completely consumed in the reaction. Now, when using that much CO, you also use:

1 mol CO X (1 mol Fe2O3 / 3 mol CO) = 0.333 mol Fe. So, you have 1.667 mol Fe remaining.