If a weak acid is 25% deprotonated at ph 4, what is the pka? if a weak acid is 25% deprotonated at ph 4, what is the pka?

pKa = 4.5

Explanation:

The weak acid can be represented by the general formula, HA and the dissociation equilibrium given as:

where HA = protonated form

A- = deprotonated form

The Henderson-Hasselbalch equation relates the pH of a solution to the ratio of the concentrations of HA and A- as;

It is given that:

% deprotonated i.e. A- = 25%

Therefore, %protonated i.e. HA = 100 -25 = 75%

pH = 4

Based on equation (1)

pKa = 4.477 i.e. around 4.5

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.