So the concentration 80% v/v equals 70% w/v.īoth 70% and 80% ethanol are used in laboratories but often the v/v or w/v is left off - watch out for this. (800 mL in a total volume of 1000 mL)īut if I take into account that the mass of ethanol is less than the mass of water then for the same volumes we get:ħ00 g of ethanol diluted to make up a total volume of 1000 mL.
If I add 800 mL of ethanol to 200 mL of water the resulting solution is 80% v/v. If I dissolve 10 g of fat in 90 g ethanol so the total mass of the whole solution is 100 g, then I have made a 10% w/w solution of fat)Īn example of a different way of expressing percent - making dilutions of ethanol in water.Įthanol diluted in water is used as a disinfectant in microbiology laboratories because diluted ethanol is more reactive than 100% ethanol (up to a point)!īut the percent is often expressed in two ways: Used where the weight of each chemical is used and not the volume (e.g. if I dissolve 10 g of table salt, sodium chloride, to make up a total volume of 100 mL of solution then I have made a 10% w/v solution of sodium chloride) Used where a solid chemical is dissolved in liquid (e.g.
if I dilute 50 mL of acetic acid by adding it to 50 mL of water there is now 50 mL of acetic acid in a total volume of 100 mL, hence the acetic acid concentration is now 50% v/v) Used where both chemicals are liquids (e.g. These variations on percentage concentration are used in chemistry and biology when making up solutions and have the following meanings.
% volume per volume (v/v), % weight per volume (w/v) and % weight per weight (w/w)
0 kommentar(er)
