Who is right?

Question

I recently did a chemistry test,
the qoestion was:

experiment A
magnesium ribbon was put in 100cm cubed acid

experiment B
magnesium ribbon was put in 50cm cubed acid and 50cm cubed dillute acid

The question was: What would be the difference in the reactions.

i wrote, no difference because both has 100cm3 acid and they both were magnesium ribbon.

my friend wrote, experiment A would be faster becasue the acid is concentrated.

we both got it right and we stayed back and asked our chemisrty teacher, thought for a while and said "go away"
lol lol lol
i didn't wanted go in more details because i got 100% and i didn't want to loose and marks.

can someone tell me who is right?

Answer 1

You were both right.

Your teacher made the question too ambiguous. Exam questions should be clearer.

The nature of the reaction is the same as you stated but it also quicker as your freind stated. As the solution is more concentrated molecular collisions happen more often, so the same reaction happens at a faster rate.

Answer 2

You caught your teacher out in a misprint, which is why he gave you the mark. If the two 50cm3 samples of acid were of the same concentration as the first, there would have been no difference. But I suspect that he should have written "+ 50cm3 water", and then got you to realise that the more dilute the acid, the slower the reaction.

Incidentally, 100cm3 of acid is a vast excess, and is enough to dissolve about a 50cm length of magnesium ribbon.

Answer 3

The question itself is flawed - '100cm cubed acid' means nothing in terms of concentration. There is no such thing as acid on its own without water, as an acid is characterised by the presence of H+ ions in aqeous solution. One must therefore assume that the'acid' is dissolved in a certain amount of water. Whether this amount is more or less in proportion to the 'dilute acid' we can never know.

Therefore, the eventual relative concentrations of the 100cm3 acid solutions in A and B can never be known and the only legitimate answer is 'we cannot tell'.

Answer 4

The teacher is right, because the question does not say if the acid is in experiment A is more concentrated than that in experiment B.

It also does not say how much magnesium ribbon was put in.

The question does not have enough detail, so you can make your assumptions, and if your conclusions are acceptable based on your assumptions, then you should get your points.

The teacher could make this a bonus question, though.

Answer 5

From the point of view of the reaction products the two would be the same. Hence you were right.
The reaction would go faster with more concentrated acid. So your friend is right.
However, for most practical purposes the difference in rate wouldn't matter since the reaction is intrinsically very fast anyway.
In each of the senses outlined you were both right!

Answer 6

you are wrong and your friend is right. If an acid is more concentrated then the reaction will happen faster, cuasing the magnesium ribbon to dissolve faster in experiment A, but thannk your teacher for marking it right.

Answer 7

What have you done? You have just told the whole world the equation that will provide the nucleus to the next generation of the latest nuclear bomb

Answer 8

acid was right bcoz it does its work properly


this was a joke
the answer is...........................................................................................................................................................................................................................................................................................................................you are wrong and your friend is right. If an acid is more concentrated then the reaction will happen faster, cuasing the magnesium ribbon to dissolve faster in experiment A, but thannk your teacher for marking it right.i think the teacher was your fan &loves u ..............................