Tris is a weak base. the basic form of tris can be written tris0 and the protonated (conjugate acid) form can be written tris. the pka of tris is 8.1. a. what is the ratio of the basic and the acidic forms of tris at ph 6.1? b. what is the useful buffering range of tris?

a) [Tris0] : [Tris] = 1 : 100

b) Range = 7.1 to 9.1

Explanation:

a) Calculation of ratio of the basic and the acidic forms of tris

pH of a buffer is calculate using Henderson-Hasselbalch equation

Conjugate acid of Tris dissociated as

For tris,

Salt or Basic form = tris0

Acid or Acidic form = Tris

pKa = 8.1

pH = 6.1

[Tris0] : [Tris] = 1 : 100

b) Range of Tris

Range of any buffer is:

From (pKa -1) to (pKa+1)

So, range of Tris is:

From (8.1 - 1) to (8.1 +1)

or from 7.1 to 9.1

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.