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### Topic: {concentration, in mol dm-3, equilibrium}  (Read 2719 times)

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#### help_me

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##### {concentration, in mol dm-3, equilibrium}
« on: September 04, 2017, 02:08:20 PM »
Water saturated with pure carbon dioxide at atmospheric pressure contains 0.15% by mass of dissolved CO2.

Calculate the concentration, in mol dm-3, of dissolved CO2 in water, [CO2 (aq)], which is in equilibrium with air containing 1% of carbon dioxide.
« Last Edit: September 08, 2017, 12:16:21 PM by Arkcon »

#### Arkcon

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##### Re: helppppp
« Reply #1 on: September 04, 2017, 04:13:57 PM »
Greetings, help_me:, I'd like to welcome you and all the new students to the Chemical Forums.  But I'd like to as you to trouble yourself to read our Forum Rules{click}. You already accepted them when you signed up for our forum, and they apply to you, whether you agree with them or not, or even if you're unaware of them.

We want to see your work, and then, we want to give you hints, so that you learn for yourself.   Let me give you some tips.  Screaming "helllppp help me" isn't cute, or cool, or impressive.  Grownups don't behave that way, or if they do, find themselves rapidly ignored.  You can begin to address this question by chinking your textbook, or class notes, for a formula that may relate the variables you know, to the answer you need.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

#### help_me

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##### Re: helppppp
« Reply #2 on: September 05, 2017, 09:42:52 PM »
Firstly, I apologise for my immaturity as I was really desperate at that time.

What I did was to find the number of moles of carbon dioxide in 100g of the solution which was 0.00340909mol and I divided it by (99.85/1000) since 99.85 is the mass of water in cm3.
However I did not manage to get the correct answer which is 3.41 x 10-4.

#### Borek

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##### Re: helppppp
« Reply #3 on: September 06, 2017, 03:33:50 AM »
Are you sure when the air contains 1% of carbon dioxide water is saturated?
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#### help_me

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##### Re: helppppp
« Reply #4 on: September 06, 2017, 11:28:54 AM »
In that case, how do I calculate the concentration of carbon dioxide in air? Is it sufficient to find the concentration of carbon dioxide that is in equilibrium with air?

Also, does it mean that the information given on the % by mass of carbon dioxide saturated in water is unnecessary in this question?
« Last Edit: September 06, 2017, 11:39:01 AM by help_me »