The absorption rates are different for each vitamin and mineral, so you can't say 98% or 20% for all.
If a nutrient in the powdered and liquid form is chemically the same and the powder or liquid does not contain substances that would stimulate or inhibit absorption, the percent of the absorbed nutrient from both forms should be about the same. Also, at the time when supplements come into the small intestine they would be all liquid because of the presence of digestive juices.
The form of a vitamin or mineral (liquid or powdered) can affect the speed of absorption -- in general, liquid forms would be absorbed faster -- but this does not necessary effect the percent of a nutrient being absorbed.
There are other factors that have much greater effect on the percent of absorption of a vitamin or mineral:
- Chemical form. For example, heme iron is better absorbed than non-heme iron
- Body stores of a vitamin/mineral. The more body iron stores you have, the less iron from supplements will be absorbed (see the source above)
- Food. Vitamin C from lemon juice stimulates iron absorption. Tannins from tea or coffee can inhibit iron absorption (see the source above).
- Amount of a supplement. The greater amount of a supplement you take, the lower percent (but not the lower amount) of it will be usually absorbed, because the absorption of certain nutrients is saturable.
- Personal differences. In different individuals, different percent of a supplement will be absorbed.