I refer to my earlier post on v/v versus w/w. I would be very grateful for any advice provided.
For 95% ethanol purchased from manufacturer, we normally take it as 95%v/v.
For 98% sulphuric acid, it seems like it is normally 98% w/w.
I have also seen a potassium hydroxide 85% (solid) labelled on a bottle and wonder what it means?
Is it usually %v/v for liquids when it is not stated on the bottle?
Thank you so much.
Personally, I think you are on a ghost hunt for I think what you are looking for doesn't exist. Other tutors may see this differently. To KNOW what the percentage means one must have it written on the label. And w/w, w/v, or v/v must be specified. If it isn't specified one doesn't KNOW. One can guess or from experience know that a 95% solution actually means 95% v/v or 95% w/w or 95% w/v. I have seen several instances where the statement is made that "in instances where it isn't stated it ALWAYS means w/w" but I have seen several instances where that isn't the case.
Perhaps Bob Pursley will comment, too.
When it comes to expressing the concentration of a solution, there are two main ways to do it: volume/volume (v/v) and weight/weight (w/w). These expressions indicate the ratio or proportion of the solute (the substance being dissolved) to the solvent (the substance doing the dissolving).
For example, 95% ethanol (ethyl alcohol) purchased from a manufacturer and stated as 95%v/v means that the solution contains 95 mL of ethanol for every 100 mL of the liquid solution.
On the other hand, 98% sulfuric acid expressed as 98% w/w means that the solution contains 98 grams of sulfuric acid for every 100 grams of the solution by weight.
Now, in the case of potassium hydroxide 85% (solid) labeled on a bottle, this refers to the concentration of the solid, not a liquid solution. It means that the solid potassium hydroxide in the bottle is 85% pure and contains 15% impurities.
When it comes to liquids, if a concentration is not stated on the bottle, it's best to refer to the manufacturer's documentation or contact them directly to inquire about the specific concentration expressed as either v/v or w/w.
In summary, the concentration expressions v/v and w/w refer to different ways of expressing the ratio of solute to solvent in a solution. The specific expression used depends on the nature of the substance being measured and the context in which it is used.