Chemistry Question Moles and Molecules

Question

Seven moles of calcium hydroxide has_____ number of Molecules

i was told the answer is 42.16*10^23

how did they get that as the answer?

Thank you

Answer 1

you should think of moles as dozens.

we use dozens to indicate 12 so if I say give me 7 dozens of eggs you just multiply 12x7

1 mole is defined by the Avogadro number (6.02214076 × 10²³ ).

In other words one mole is equal to 6.02214076 × 10²³ .

long story short, This number was created to find a way to calculate the number of molecules or atoms since they are extremely small.

One mole of calcium hydroxide then is made of 6.02214076 × 10²³ molecules.

multiplying this number by 7 you get the 42.16 x 10^23 molecules.

Answer 2

Hi Gabrielle W.,

You should know by this time in your course that a mole has a certain (Avogadro's Number) number of molecules to it. Just multiply that value by 7.

I'm a little sceptical that Ca(OH)₂ can be described as molecules, and you should be too -- it's an ionic solid in a lattice, so not really as individual molecules as a solid, and dispersed as ions if dissolved, hence not as individual molecules there, either. If you try to vaporize it, you'll probably end up with clusters of ions or even dehydrate to CaO.

I'm not saying that it's a useless material, for all that -- great for dissolving bodies, bones and all, hence a useful ingredient in creepy murder mystery literature.

But for ordinary uses, CaCO₃ is more common -- marking athletic field lines on grass, cross-country running courses, etc.

-- Cheers, -- Mr. d.