ashna
molarity and molality !
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waterineyes
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See there your question is given like:
2g of a Substance is added to water...
Can you tell me what is solute here and what is the solvent here ??
ashna
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solvent is water and solute is that 2g substance .. correct ?
waterineyes
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Yes..
waterineyes
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For finding molarity you need number of moles solute..
How will you find number of moles of solute because it is given in 2 grams.. ??
ashna
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i dont know !
waterineyes
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For that there is a formula you will use that..
ashna
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ah .. that previous one ?
ashna
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derived from molarity .. ?
waterineyes
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\[Number \; Of \; Moles = \frac{Grams \; Present}{Molecular \; Mass \; Of \; that \; Substance}\]
waterineyes
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No no that one..
This one I have written above now..
ashna
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how many formulas are there in this chapter ?
waterineyes
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Now let us try to implement this formula on a question so that you can understand it properly.
There are as many formulas as there are hairs on your head..
Ha ha ha..
ashna
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what if am bald ?? :P
waterineyes
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Wait for one second my mummy is calling me..
Have a look on that formula and try to memorize it and understand it as well..
ashna
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okay !
waterineyes
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Then there are as many formulas as there are hairs on my head
And I don't like to be bald..
ashna
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am not bald either .. i were just kidding :)
ashna
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|dw:1345436660852:dw|
waterineyes
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Mention me when you will come..
I am in Mathematics Section..
ashna
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yeah back !
ashna
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@waterineyes
waterineyes
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I have to go ashna...
waterineyes
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So let us hurry up I can explain you this thing..
ashna
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okay
waterineyes
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See you are given with question like this:
2g of a NaCl is dissolved in 4 L of water.. Find the Molarity..
waterineyes
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Hurry up find the molecular mass of NaCl first..
waterineyes
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Because you have to find Number of Moles first..
ashna
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23+35.5 ?
waterineyes
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Yep...
waterineyes
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so it is 58.5..
ashna
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58.5
waterineyes
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Now 2g you are given with..
Can you find number of moles now ??
ashna
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2 / 58.5
waterineyes
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Yep solve it hurry up..
ashna
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0.034...
waterineyes
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Yep..
waterineyes
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Now can you find molarity by using its formula ??
waterineyes
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For that you need volume of solution too..
ashna
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0.034 / 4
waterineyes
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For that you need volume of solution too..
waterineyes
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No..
ashna
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then ?
waterineyes
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I don't know..
Ha ha ha..
waterineyes
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Yes we can ashna..
ashna
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okay .. you leave then !
waterineyes
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For that you should know the density of water..
It will be given to you..
I think approximately density of water is 1..
So:
\[Density = \frac{Mass}{Volume}\]
waterineyes
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Oh god what I am doing..
We have to find volume of NaCl not water..
ashna
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you better leave water ..
waterineyes
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Yeah but I will explain you after coming for sure..
May be till then others may help you..
Or I think I have written the question wrong...
ashna
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hm..
waterineyes
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But the main concept is you got how to find number of moles of solute when it is not given..
Right ??
ashna
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yes
waterineyes
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It did increase some knowledge of yours.
Okay now I have to leave..
There is work for me from my neighborers..
So I have to go now..
ashna
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hm.. bye
waterineyes
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Bye take care as well..