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# Any mathematicians around?

Using the formula (W/V), say I want to make a 0.5% solution I would mix 1g of salt with 199ml of water right.

If I wanted to turn this % solution into molarity would the answer be 87mmol?

how did you get that figure?

For the concentration I get 0.086 dm-3 (dm to the power of minus 3)

Oh yeah and then multiply it by 1/1000 = 86mmol, so it seems right to me :thumbsup:

Original Poster

Which figure?

Civic EG6;8519449

Which figure?

87? :roll:

Original Poster

Rep+

Did you use the full molar mass of NaCl i.e. 58.443? Because I used just 58 and got the answer 87.

Civic EG6;8519502

Rep+ Did you use the full molar mass of NaCl i.e. 58.443? Because I used … Rep+ Did you use the full molar mass of NaCl i.e. 58.443? Because I used just 58 and got the answer 87.

I used 58.5 - my periodic table has Chloride as 35.5 :thumbsup:

You do not need a mathematician but a chemist-from my A level chemistry i think as follows:

Weight to volume ratio for 0.5% solution of sodium chloride you need 1g of sodium chloride in 200ml of water or 0.5g in 100ml of water.

To calculate molarity you need to determine the number of moles of NaCl in 1g=1/58.5=0.0170mol.
THis is in 200ml of water. Molarity is based on moles in 1000ml, so molarity = 0.0170*1000/200 =0. 08547 M

Then convert to mmol.