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Topic: Concentration  (Read 7988 times)

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Offline jsmith613

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Concentration
« on: June 02, 2010, 11:25:19 AM »
If we take two solutions of Hydrochloric acid and react them with 10g of CaCO3 chips of the SAME surface area:

solution A has HCl (aq) at 1 mol/dm-3 (concentration of 1 mol)
Solution B has HCl (aq) at 0.5 mol/dm-3 (concentration of 0.5 mol)

will solution A produce double the amount of products than solution B due to the fact the conc. is double (more acid particles per cm3)?

Offline sjb

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Re: Concentration
« Reply #1 on: June 02, 2010, 12:49:59 PM »
I guess that would depend on the volumes of each solution that you had.

How much product would you get if you had 10 ml of solution A? 10 ml of solution B? 10 litres of solution A? Of B?

Offline jsmith613

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Re: Concentration
« Reply #2 on: June 02, 2010, 01:19:20 PM »
I guess that would depend on the volumes of each solution that you had.

How much product would you get if you had 10 ml of solution A? 10 ml of solution B? 10 litres of solution A? Of B?

The question is more generalised.
Presuming you had EXACTLY the same volume of acid, EXACTLY the same mass of CaCO3 with EXACTLY the same SA (basically everything IN BOTH experiments is IDENTICAL) except for the concentration.

If you had two concentrations

a) 1 mol
b) 0.5 mol

would the 1 mol solution produce MORE GAS than the 0.5 mol solution if ALL other conditions are identical.

Thanks

Offline sjb

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Re: Concentration
« Reply #3 on: June 02, 2010, 04:54:08 PM »
In some cases, yes you would get more gas from the 1.0M solution than the 0.5M, but not others, do you appreciate why?

Offline OrganicSynthesis

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Re: Concentration
« Reply #4 on: June 02, 2010, 07:44:08 PM »
Don't forget to accounting for whether CaCO3 is limiting or not. ^^

Offline jsmith613

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Re: Concentration
« Reply #5 on: June 03, 2010, 03:44:52 PM »
In some cases, yes you would get more gas from the 1.0M solution than the 0.5M, but not others, do you appreciate why?

No, i dont understand why

Please could you explain

Offline Borek

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Re: Concentration
« Reply #6 on: June 03, 2010, 04:04:02 PM »
Do you know what a limiting reagent is?
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Offline jsmith613

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Re: Concentration
« Reply #7 on: June 03, 2010, 04:30:36 PM »
Do you know what a limiting reagent is?

Yes.
Lets say you had excess Acid and 5 g of CaCO3
the CaCO3 would be the limiting reagent


Offline jsmith613

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Re: Concentration
« Reply #8 on: June 03, 2010, 04:31:58 PM »
Oh. I see, so with lower conc. acids, the acid becomes the limiting reagant.

Nonetheless, if 5 cm3 of acid reacts with 5g of CaCO3 chips, no matter if the acid is or is not the limiting reagant, less gas would be given off
RIght?

Offline sjb

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Re: Concentration
« Reply #9 on: June 03, 2010, 04:35:08 PM »
Do you know what a limiting reagent is?

Yes.
Lets say you had excess Acid and 5 g of CaCO3
the CaCO3 would be the limiting reagent



So, returning to my original question
I guess that would depend on the volumes of each solution that you had.

How much product would you get if you had 10 ml of solution A? 10 ml of solution B? 10 litres of solution A? Of B?

Which is the limiting reagent if you had 10 ml of each solution? What about 10 litres?

Offline jsmith613

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Re: Concentration
« Reply #10 on: June 03, 2010, 04:50:00 PM »
Quote
Which is the limiting reagent if you had 10 ml of each solution? What about 10 litres?

OK, this is what I would presume - I have not actually conducted the expt.

10ml

0.5 moll: Acid
1 mol: CaCO3

10 l

CaCO3 in both cases

So, if we presumed we were using a 10l solution, where the mass of CaCO3 was constant, would 1 mol give off more gas?

Thanks

Offline sjb

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Re: Concentration
« Reply #11 on: June 04, 2010, 02:07:53 AM »
Quote
Which is the limiting reagent if you had 10 ml of each solution? What about 10 litres?

OK, this is what I would presume - I have not actually conducted the expt.

What's the balanced equation for the reaction you are (hypothetically) carrying out?


10ml

0.5 moll: Acid
1 mol: CaCO3

10 l

CaCO3 in both cases

So, if we presumed we were using a 10l solution, where the mass of CaCO3 was constant, would 1 mol give off more gas?

Thanks

If, as you suggest, in the 10 litre case the CaCO3 is the limiting reagent then the amount of gas would be limited by that, and so in both the 1M and 0.5M case you should give off the same amount of product.

Offline jsmith613

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Re: Concentration
« Reply #12 on: June 04, 2010, 06:34:33 AM »
Quote
What's the balanced equation for the reaction you are (hypothetically) carrying out?
CaCO3 (a) + HCl (aq)  :rarrow: CaCl2 + H2O + CO2

Quote
as you suggest, in the 10 litre case the CaCO3 is the limiting reagent then the amount of gas would be limited by that, and so in both the 1M and 0.5M case you should give off the same amount of product.
OK, so lets say the acid was the reagent, would different volumes of gas be given off then.

Thanks

Offline sjb

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Re: Concentration
« Reply #13 on: June 05, 2010, 10:41:15 AM »
If the CaCO3 was in excess in both cases, then yes, the same volume of 1.0M and 0.5M HCl would produce different quantities of products.

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