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# Preparing Solution [WARNING: HARD ONES] watch

1. How you would prepare these solutions?? I couldn't find anyone else to help and these are for tomorrow... Show the working out and explain! Ill try and understand

Note: All solutions must be prepared in water!

1. 10mg/ml malaic acid potassium salt (C4H3O4K) in a total volume of 50ml.
2. 5g/L sodium bicarbonate (NaHCO3) in a total volume of 2L.
3. 0.01M dipotassium hydrogen phosphate (K2HPO4) in a total volume of 250ml.
4. 2M sodium chloride (NaCl).
5. 100ppm lead (Pb) in 1000ml.
6. 0.1M sodium chloride (NaCl) and 0.5M potassium chloride (KCl) in a total volume of 5L.
7. Mobile phase containing 70% buffer (prepared by you earlier) and 30% methanol. The total volume should be 1000ml.
8. A 5 millimolar solution of glucose (C6H12O6)
2. (Original post by Prospekt117)
1. 10mg/ml malaic acid potassium salt (C4H3O4K) in a total volume of 50ml.
2. 5g/L sodium bicarbonate (NaHCO3) in a total volume of 2L.
7. Mobile phase containing 70% buffer (prepared by you earlier) and 30% methanol. The total volume should be 1000ml.
cmon, these three are simple math

(Original post by Prospekt117)
3. 0.01M dipotassium hydrogen phosphate (K2HPO4) in a total volume of 250ml.
4. 2M sodium chloride (NaCl).
6. 0.1M sodium chloride (NaCl) and 0.5M potassium chloride (KCl) in a total volume of 5L.)
8. A 5 millimolar solution of glucose (C6H12O6)
No moles = concentration x volume (in dm3)
Mass = no moles x Mr

input the values to get the mass needed for the given amount of DW.

(Original post by Prospekt117)
5. 100ppm lead (Pb) in 1000ml.
A harder one, 100ppm means 100g of lead per 1,000,000g of solution, which works out as 0.01% w/v, 1% w/v would mean 1g of lead in 99g of water, so what is 0.01%?
3. Could you show me the calculations please? It takes a second to you and it could save me! I will work them out myself afterwards!
4. i have the exct same assignment questions and also have no idea! if someone could help with the answers and how you got to them we'd be most grateful!
5. Where are you from? ^^
6. teeside i honestly am ridiculously stuck with this and the deadlines tommorow!
7. Are you at Northumbria Uni??
8. Tee hee "hard ones" oh my immaturity!

9. no one type the answers

seriously though, it takes 2 secs to answer them urself......
10. (Original post by Prospekt117)
Are you at Northumbria Uni??
Wait, you're at uni and you can't answer these??
11. Guys I know you wish to help us and teach us but this is urgent! I have other assignments like these for the holidays and I will learn to do these on my own! But THIS assignment is for tomorrow! And its a small part of a huge essay about solutions! Anyway I can work out the first ones but these:

3. 0.01M dipotassium hydrogen phosphate (K2HPO4) in a total volume of 250ml.
4. 2M sodium chloride (NaCl).
6. 0.1M sodium chloride (NaCl) and 0.5M potassium chloride (KCl) in a total volume of 5L.)
8. A 5 millimolar solution of glucose (C6H12O6)
No moles = concentration x volume (in dm3)
Mass = no moles x Mr

input the values to get the mass needed for the given amount of DW.

5. 100ppm lead (Pb) in 1000ml.

A harder one, 100ppm means 100g of lead per 1,000,000g of solution, which works out as 0.01% w/v, 1% w/v would mean 1g of lead in 99g of water, so what is 0.01%?
Might require some more help! (ps we are doing the foundation year at Uni)
12. Using the equations i have showed you, you could have done these calculations in the amount of time you have spent asking others to do it for you.

e.g.

1. is 10x50......

3. is 0.01x0.25xMr of the compound

Help is one thing, doing the work for you is another.
13. I dont need the work done, I need to know the method! What is the method and whats the working out?! ll +rep rape whoever gives me a straight simple answer instead of putting all those philosofical b****t on how I should do this on my own etc. I wouldnt ask on a forum if I had time to do this on my own, stop lecturing around and trying to be the freakin sensei of karate kid, and I will be forever grateful!
14. hey, i've pretty much worked three through for you and SHOWED you the method

For the concentrations in M, use
mass = Mr x concentration x volume/dm3
and the volume of water as the volume of the solution

For the concentrations in mg/ml or mg/L just times the volume by the concentration to get the mass you need

For the ppm (the only hard one) you want a total mass of 1000g (for a volume of 1000ml), of which 0.01% has to be lead and 99.99% has to be water.
15. Thanks a lot!!!

Ok lets see number 3 is

166.08 x 0.25 x 0.01 = 0.4152

Whats the unit? is it grams?

Ill work out the others! Can you suggest a way I can write these in the essay? I mean the format (I cant put: in 1 mole of HerpDerp there are 168 grams of HerpDerp so....)
16. the mass will be in grams. Something like "to make 0.01M K2HPO4 solution dissolve 0.415g of solid K2HPO4 salt in precisely 250ml of distilled water", not sure how detailed you need your instructions to be?

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Updated: December 9, 2010
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