I need a quick reply please. Thank you in advance.

I don't know that they are the correct answers. But, you might want to look down at the bottom of this page for links to questions that have been similar to yours.

Their chemical compounds put an even number of valence electrons in the outter shell hence they do not react much.

Appls isn't right they do react, I think they are thinking about ionic interactions. In covalent interactions (such as this) it doesn't matter if they have similar numbers of valence electrons. Think of an oxygen molecule (O2) both oxygens have identicle amounts of valance electrons yet they definitely react and form a molecule.

To the OP the key to your answer is think how they react - what do they rely on.
Here's some clues dilute sulphuric acid
What makes something acidic?
What will you have less of if it is dilute?
Work that out and you'll have your answer.

Ok thanks for trying

Argh, I've been looking at this in too much of a chemical mechanics bent does your question linked to limestone being dissolved on buildings and cliffs?

If so this is a more probably answer...
One of the products is not very soluble (clue it's not the gas or water) It can inhibt the reaction via coating the Calcium carbonate.

I can't be sure which is the answer your teacher wants, which one seems more relavent to your studies?

Ok I let you know afterwards. Its on the chapter metals in fact, topic 'Reaction of acids on Metal Carbonates'. It is told that metal carbonates generally react with acids to form a salt, water and carbo dioxide.

It said that " However lumps of Calcium Carbonate hardly reacts with dilute sulphuric acid. WHY?"

Perhaps the word lumps is a hint. Actually I have 2 hypotheses:
I) Either the salt product stays on the surface and thus prevent any further reactions,
ii)Or that calcium carbonate, being up the reactivity series, forms a very stable carbonate which is difficult to react with the acid.

Anyway I think that I will get the answer by next Sat (24 Nov).

If anything says lumps always mention surface area first for easy marks then go onto the more complicated answer. I think your answers are good. It is the stable salt which forms an unreactive layer as far as I can remember - it's been a loooooong time but it is coming back slowly. :P

Have you got exams soon or do you get them all in the summer? Either way good luck with your studies.

Thanks

The first hypothesis was the correct one.

I got my nswers from here for my homework and I neva had a clue what the question meant