You are making a lactated Ringer's solution. Procedure calls for 20g of lactic acid per liter. What is the %

Question

of lactic acid? Last question that I had trouble with relating to my online pharm tech class. Please show work to help with future similar problems.

Answer 1

If you had one litre of pure water, it would weigh 1 kilogram (1mL of water = 1gram, so 1 litre is 1kg). But you have 20g of lactate in 1 litre of aqueous solution. This is referred to as 2% lactate (since 20g is 2% of 1000g). This is also written as 2% lactate w/v. "w/v" means "weight/volume" - you just take the weight of the stuff (in grams) you have dissolved in your aqueous solution (in this case 20g), and divide it by the volume (in mL) that it's in (in this case 1000mL), then multiply that by 100 to get the percentage.