Answer:they should take, 5.0M NH3 and 8.0M K2CO3 each, that is option (d) and (e).
But, if we are to choose between one of them; 8.0 M K2CO3 will be the best answer.
Explanation:
Generally, a base is a substance that completely ionized in an aqueous solution or a base may be defined as a substance which accepts hydrogen ions(this is according to Bronsted-Lowry definition of base).
What then is a weak base?.
A weak base is a substance that that does not fully ionize in an aqueous solution or a weak base is a substance that does not convert to hydroxide ion fully in a solution.
For instance, A weak base from the question above is Ammonia,NH3. When Ammonia, NH3 is reacted with water (the reaction is a reversible reaction) which gives hydroxide ion, OH^- and Ammonium ion, NH4^+. The Ammonia here, is not fully converted into Hydroxide ion.
From the question, the laboratory director want both student to select a bottle of a concentrated weak base. Check this 'CONCENTRATED WEAK BASE' not just any base or any weak base but a concentrated one.
For option (a): 7.0M Sodium Hydroxide, NaOH; sodium hydroxide is a strong base, so this is wrong.
For option (b): 0.03 M Ammonia,NH3. Ammonia is a weak base. Here, we have a 0.03 M, which means that it IS LESS CONCENTRATED.
For option (c): 0.1 M NaOH, Sodium hydroxide is a STRONG BASE.
For option (d) and (e): both Ammonia and potassium carbonate are weak bases. And with 5.0 M and 8.0 M respectively, we can see that they have high concentration. So, both are correct.
