Question #2420c

2 Answers
Aug 8, 2016

Answer:

The Kb determines if a compound is a weak base or a strong base. Also the determination of pH or POH can determine if s compound is a strong or weak base.

Explanation:

A strong base has a large number of basic ions OH- in solution. A weak base has a small percentage of basic ions OH - in solution.

Ph 8-10 are weak bases, Ph 11-14 are strong bases.

H+ + OH- = 14

in water H+ = # 10^-7# and OH- = #10^-7#

At Ph 13 for example H+ = #10^-13# while OH- = # 10^-1

The total must always equal #10^-14#

OH- #10^-1# means that 1/10 molecules is a OH- ion 10% of the solution that makes it a strong base.

pH 8 means that OH- = # 10^-8#

#10^-8# = 1/00000000 of the solution are OH- ions. That makes it a weak base.

Aug 26, 2016

Answer:

The #K_b# determines if a compound is a weak base or a strong base.

Explanation:

A strong base dissociates completely in solution (has a #K_b ≫ 1#).

A weak base dissociates slightly in solution (has a #K_b ≪ 1#).

A base can be a strong base, even if it contributes only a few ions to the solution.

Thus, #"NaOH"# is a strong base because it dissociates completely:

#"NaOH(aq)" → "Na"^+"(aq)" + "OH"^"-""(aq)"#

If you dissolve #10^"-8" color(white)(l) "mol of NaOH"# in 1 L of water, it will contribute only #10^"-8"color(white)(l) "mol"# of #"OH"^"-"# ions, but that is 100 % of what it has to give.

#"NaOH"# is a strong base. Its strength does not depend on its concentration.