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Hi all
I have to ask a quick question here, everyone in science here have gone home sick or not here and there is noone to ask. I need to make 10% glucose and 20% salt what Molars are 10% and 20%? Please help THANKS

Hi Tammie
Why don't you just make up 10g in 100ml for glucose and 20g in 100ml for salt?

Do you actually need the molarity?

Lorrae

Hi Tammy,

From 'The Laboratory' (Pg 3):
PERCENTAGE SOLUTIONS
Weight per volume w/v
Definition: Grams of solute per 100mL of solution
eg. to make a 10% sodium chloride solution, dissolve 10g of NaCl in water and make up to 100mL
Volume per volume v/v
Definition: mls of a specific liquid per 100mL of solution
eg. for 70% alcohol solution, add 70mL of alcohol to 30mL water. Total volume = 100mL.

Cheers,

tHANK YOU SO MUCH I DONT NEED THE MOLARITY BUT ITS GOOD TO KNOW THEM NOW THANK YOU ALL AGAIN THIS IS A GREAT SITE

M. Molarity is the number of moles of a solute dissolved in a liter of solution. A molar solution of sodium chloride is made by placing 1 mole of a solute into a 1-liter volumetric flask. (NaCl Molecular weight 58.44). Weigh 58.44 gr of NaCl water is then added to the volumetric flask up to the one liter line. The result is a one molar solution of sodium chloride. To make 20% NaCl you used 116.88 gr thus 2M.

Glucose 10% The molarity of a solution is calculated by taking the moles of solute and dividing by the liters of solution.

Glucose =180 gr/mol
To make 10% solution you used 18 gr.
18/180=0.1
0.1/1 =1M

Just to clarify this, %solution is a different measure of concentration to M solutions.
10% salt solution is made up of 10g of salt into 100mL volumetric flask (or 100g into 1000mL flask), but 1M is 58.44g of salt into 1000mL flask, which is only 5.8%solution.
Hope this makes sense.'
Lada