Chemistry Q atomic weight

TirNaNog.

Does the atomic weight of an element determine how much H2 gas is liberated in a metal - Hcl reaction??
For example would calcium liberate more H2 gas than magnesium??

Kevster

.... ....Your question is rather vague. However, it'd be more to do with the charge-state of the metal. Calcium is 2+ in it's general form, as is Magnesium. Would these even react with Hydrogen therefore!? The H atom is 1+.

+ and + don't match


??

TirNaNog.

Kevster wrote: »

.... ....Your question is rather vague. However, it'd be more to do with the charge-state of the metal. Calcium is 2+ in it's general form, as is Magnesium. Would these even react with Hydrogen therefore!? The H atom is 1+.

+ and + don't match


??

Yes they do react with hydrochloric acid.
they displace the Hydroygen in the HCl?? dont they??

craggles

They will both react with HCl. The difference is the speed, or rate of the reaction.

They will produce the same amounts of Hydrogen gas but one will take longer than the other. The Calcium is more reactive so the reaction will go quicker if you use Calcium.

The reason for Calcium being more reactive is not the atomic weight though. :pac:

TirNaNog.

craggles wrote: »

They will both react with HCl. The difference is the speed, or rate of the reaction.

They will produce the same amounts of Hydrogen gas but one will take longer than the other. The Calcium is more reactive so the reaction will go quicker if you use Calcium.

The reason for Calcium being more reactive is not the atomic weight though. :pac:

Why do they liberate the same amount of H2 gas?because they are both 2+ valencys?and why does Aluminium liberate even more H2 gas again?because Al valency is 3+ and Cl is -1?
Thanks

Kevster

Im learning things here too. I imagine that they produce the same amount of H2 gas because they bind the same amount of Oxygen atoms atoms. like, if you have the same amount of Ca and Mg, then you'll get the same amount of H2 gas after allowing them to react separately with the HCl.

However, I'm not entirely sure why it was mentioned that Ca would produce the gas more quickly. It could be that it's just more reactive (as he said), and therefore would be due to the actually configuration of the electrons in the different orbitals (I guess). Mg has a full outer shell, but Ca's is only partially occupied.

??

Kevin

craggles

TirNaNog. wrote: »

Why do they liberate the same amount of H2 gas?because they are both 2+ valencys?and why does Aluminium liberate even more H2 gas again?because Al valency is 3+ and Cl is -1?
Thanks

Aluminium on its own wouldn't liberate even more H2 gas, the amount of H2 gas released depends entirely on the amount of HCl because that's where the Hydrogen gas is coming from.

Unless you were talking about an Aluminium compound with Hydrogen in it that gets released, but that would be a different reaction altogether if that was the case. Hope that doesn't confuse you.

Kevster wrote: »

Im learning things here too. I imagine that they produce the same amount of H2 gas because they bind the same amount of Oxygen atoms. like, if you have the same amount of Ca and Mg, then you'll get the same amount of H2 gas after allowing them to react separately with the HCl.

However, I'm not entirely sure why it was mentioned that Ca would produce the gas more quickly. It could be that it's just more reactive (as he said), and therefore would be due to the actually configuration of the electrons in the different orbitals (I guess). Mg has a full outer shell, but Ca's is only partially occupied.

??

Kevin

That's right yeah.

Yes, Calcium is more reactive, that's basically all there is to it. According to the octet rule neither of them have full outer shells though, they both have 2 electrons in the outer shell. Overall it's the same reaction in both cases but Calcium is just more reactive.

TirNaNog.

Hi its Aluminium foil(kitchen foil) so how would it liberate more h2 gas?

craggles wrote: »

Aluminium on its own wouldn't liberate even more H2 gas, the amount of H2 gas released depends entirely on the amount of HCl because that's where the Hydrogen gas is coming from.

Unless you were talking about an Aluminium compound with Hydrogen in it that gets released, but that would be a different reaction altogether if that was the case. Hope that doesn't confuse you.



That's right yeah.

Yes, Calcium is more reactive, that's basically all there is to it. According to the octet rule neither of them have full outer shells though, they both have 2 electrons in the outer shell. Overall it's the same reaction in both cases but Calcium is just more reactive.

Kevster

How are the orbitals filled? It's been a long time since I did chemistry.

1s2 (2 e-)
2s2 (2 e-)
2p6 (6 e-)
3s2 (2 e-)
3p6 (6 e-)

??

TirNaNog.

Kevster wrote: »

How are the orbitals filled? It's been a long time since I did chemistry.

1s2 (2 e-)
2s2 (2 e-)
2p6 (6 e-)
3s2 (2 e-)
3p6 (6 e-)

??

yes thats correct
3p can be broken down into 3 subshells of 3px 3py 3pz

cianl1

This thread doesn't make sense anymore!

If you're using aluminium foil, i.e. pure aluminium, then the hydrogen gas liberated must only come from the HCl.

Calcium and magnesium do not have full outer shells. Their configurations are:

Ca: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2 (p-orbitals are not filled, hence not full outer shell)
Mg: 1s2, 2s2, 2p6, 3s2 (same story, p-orbitals not filled)

Both will produce the same amount of H2 gas but as craggles said, the reaction with Ca will go faster, this is due to it being higher up in the reactivity series than Mg. It is also known that the further down a group you go, the more reactive the element.

Note: Not trying to be a prick just needed to straighten things out in my head.

Kevster

cianl1 wrote: »

This thread doesn't make sense anymore!

If you're using aluminium foil, i.e. pure aluminium, then the hydrogen gas liberated must only come from the HCl.

Calcium and magnesium do not have full outer shells. Their configurations are:

Ca: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2 (p-orbitals are not filled, hence not full outer shell)
Mg: 1s2, 2s2, 2p6, 3s2 (same story, p-orbitals not filled)

Both will produce the same amount of H2 gas but as craggles said, the reaction with Ca will go faster, this is due to it being higher up in the reactivity series than Mg. It is also known that the further down a group you go, the more reactive the element.

Note: Not trying to be a prick just needed to straighten things out in my head.

Thanks for clearing it up, especially the orbitals thing. You can't really blame me though as I've been a microbiologist for the past three years!

Kevin

cianl1

Kevster wrote: »

Thanks for clearing it up, especially the orbitals thing. You can't really blame me though as I've been a microbiologist for the past three years!

Kevin

Don't worry about it. As a sciencetist (yes, I did that on purpose), I'm committed to informing people about my field of choice and correcting mistakes and misconceptions held by individuals.

In short...

I am a superhero.
I... AM... BATMAN!

TirNaNog.

I was just saying in general the P shell can be broken into x y and z I wasnt refering to the elements used,
anyway Al liberated more H2 because of its valency was different than the other 2 I take it

cianl1

Where are you getting this from, don't mind me asking?

TirNaNog.

An experiment,
Al produced alot more H2 gas than the other 2,
using the same amount in grams(say 10g) out of the 3 metals
10g of Al =more moles of metal
balance the equation like?

cianl1

Could you give the full question? That seems to be missing some info.

TirNaNog.

Ask me bollix.:pac:

cianl1

Just trying to be a helpful sort of gent. Don't bite my arm off, whatever you do.

Marvinthefish

I'm thoroughly confused (as is often the case)

2Al + 6HCl --> 2AlCl3 + 3H2

is the reaction, yes?

Then once you have the same number of moles of metal (say 27g aluminium or 40g of calcium) then you will get the equivalent number of moles of H2 gas. So, from the equation if you have two moles of metal (whatever metal, it doesn't matter once it reacts) you will get three moles of H2 gas!

TirNaNog.

Marvinthefish wrote: »

I'm thoroughly confused (as is often the case)

2Al + 6HCl --> 2AlCl3 + 3H2

is the reaction, yes?

Then once you have the same number of moles of metal (say 27g aluminium or 40g of calcium) then you will get the equivalent number of moles of H2 gas. So, from the equation if you have two moles of metal (whatever metal, it doesn't matter once it reacts) you will get three moles of H2 gas!

the mole ratio of Al to H2 is different
than the mole ratio of Ca to H2

cianl1

It would help if you gave the balanced equations for the reaction then. Then we can point you in the right direction.

Marvinthefish

Your original Q was "does atomic weight affect the amount of H2 gas you get?" (paraphrasing). If you start with the same number of moles of metal the answer is...

no

.

Edit: Just found the equivalent calcium equation, so I see what yoou mean about the different mole ratios TirNaNog

2HCl + Ca ----> CaCl2 + H2

That was like pulling teeth

TirNaNog.

I had it all sussed out days ago thanks
The initial question was to determine the atomic weight of the 3 elements by the amount of H2 gas produced.

SOL

Hold up the show here, there have been a whole number of serious misunderstandings so there are a few things we need to clarify.


Firstly when we talk about ammounts there are different quantities we could be talking about. If we are talking about moles of Calcium vs magnesium, then that is a different thing to grams.
So 1 mole of Magnesium weighs 24.31g, for calcium it weighs 40.08g

so when we talk about ammounts, we have to specify what we mean, but in short this means that one mole of Mg and one mole of Ca will in excess HCl liberate the same ammount of Hydrogen. But since calcium has a higher molar weight it will give of less hydrogen gram for gram against magnesium.


Next post will be about reactivity and stoichiometry... stay tuned.