I seemingly can't solve the following problem, I've spend over 30 mins on it, no progress, can any of you geniusses give a step by step solution to me? Thank you so much


A mixture of aluminium and iron weighing 9,62g reacts with hydrogen chloride in aqueos solution according to the parallel reactions

2Al + 6HCL --> 2AlCl3 + 3H2 Fe + 2HCL --> FeCl2 + H2

A 0,0738 quantity of hydroen is evolved when the metals react completely. Calculate the mass of iron in the original mixture.

Here's the solution I found on Slader.com

1) x + y = 9.62g; Considering that x is a mass of Al, and y is the mass of Fe

2) enter image description here ; Ar (Al) = 26.98 g/mol ;Ar (Fe) = 55.85 g/mol

3) enter image description here ;; enter image description here

4) enter image description here ;;

5) 0.0556x + 0.0377y = 0.366

x + y = 9.62 (multiplying with 0.0566)

0.0566x + 0.0566y = 0.535

Substracting this two equations

0.0377y = 0.169

y = 4.48 g Fe

6) x + 4.48 = 9.62

x = 5.14 g Al


Can someone explain step 5 to me? I really don't understand how one gets the "0.0377y = 0.169".

Thanks so much!!


Well, I understand it, but I don't like it. There's an error in line 5 of eq 5.

When you subtract the two equations, put everything in writing:

0.0556x + 0.0377y - 0.0566x -0.0566y = 0.366 - 0.535

Then -0.0189y = -0.169, (not 0.0377y = 0.169)

Then y = 8.94g (Fe) (answer)

(And incidentally, x + y = 9.62g, so x = 0.68g (Al))

I sympathize with you - but taking a little shortcut sometimes makes it difficult to detect an error. Sometimes you just have to write out everything.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.