What are some examples of quantitative and qualitative measurements?

2 Answers
May 9, 2014

Quantitative measurements are those that deal with a quantity, for example:
Mass of as sample
Length of a piece of wire
Molecules in a mole
Volume of a gas
Temperature of a sample

These types of measurements are called Extensive.

Qualitative measurements are those that deal with the quality, for example:
Color of a sample
Texture of a surface
Coarseness of a powder
Aroma of a reaction
Malleability of a metal

These types of measurements are called Intensive.

I know this is a simple explanation but still I hope it is helpful.

To give a more chemical example, quantitivative analysis will tell you how much of something there is in your sample whereas qualitative analysis will tell you what is in your sample.


As an example, if you pour potassium thiocyanate (#KSCN#) in a solution and it goes blood red, it's sign that you have a iron III ions in that solution, according to the reaction

#Fe^(+3) + 6SCN^(-) rarr Fe(SCN)_6^(-3)#

In which the complex in blood red. This is qualitative because it tells you there is some amount of (free) iron III ions in that solution but doesn't tell you how much.

But if you pour an excess of #NaOH# in a solution with iron III ions, filtrate the caramel precipitate, calcinate it and weight it, you'll know how much iron III ions were in that solution according to the reaction

#Fe^(+3) + 3OH^(-) rarr Fe(OH)_(3(s))#

#2Fe(OH)\_(3(s)) rarr Fe_2O_(3(s)) + 3H_2O_((g))#

So by weighting the #Fe_2O_3# you can know how much #Fe^(+3)# were there in the original solution and easily calculate concentration.

It's important to note though, that in a real life analysis you always do a qualitative one before a quantitative one. (Or at least someone else does and tell you the results).

This is because quantitative analysis need to only react with whatever your compound of interest is, so if you did that test I mentioned with the iron above in a solution that had #Cr^(+3)#, which also precipitates, there'd be an error.