What is the approximate ph of a 0.10 m solution of a weak acid that has a ka of 5 x10^-5 m?

pH = 2.66

Explanation:

weak acid:

∴ Ka = 5 E-5 M = [H+][A-]/[HA]

∴ [HA] = 0.10 M - [A-]

∴ [H+] = [A-]

⇒ Ka = [H+]²/(0.10 - [H+])

⇒ [H+]² + 5 E-5[H+] - 5 E-6 = 0

⇒ [H+] = 2.211 E-3 M

⇒ pH = - Log [H+]

⇒ pH = 2.6553

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance

the awnser is group 12