In: Biology
WHICH OF THE FOLLOWING REACTIONS REPRESENTS A STRONG ACID?
A. HCl ---> H+ +Cl-
B. NH3 + H+ <-----> NH4+
C. H2CO3 <----> HCO3- + H+
D. NaOH ---> Na+ +OH-
A solution has a pH of 1.0 x 10^(-2)M. What best describes the solution?
BASIC
ACIDIC
SALTY
NEUTRAL
(1) (A) is the correct answer.
Acid is a substance that releases H+ ions in water and base is a substance that takes up hydrogen ions present in a solution.
A strong acid is one which dissociates completely in water. Dissociation refers to breaking down to produce H+ ions.
Also, a strong acid produces a weak conjugate base(the ion produced after acid dissociation along with H+ ion). A weak base is one which do not accept proton from H3O+; i.e, the reverse reaction does not occur.
Strong acids release all H+ ions in them, whereas weak acids do not release all the H+ions.
In option (A), HCl dissociates completely releasing H+ and Cl- ions. All HCl molecules dissociate completely in solution.
Cl- is the conjugate base that do not accept H+ readily. So, HCl is a strong acid.
In (B), NH3 accepts an H+ and forms NH4+ ion.
Since NH3(ammonia) accept H+ ions, it is a base.
In(C), H2CO3 do not dissociate completely; it releases only one H+ ion and HCO3- ion.
A weak acid produces a strong conjugate base; meaning that the base has high affinity for H+ and reverse reaction takes place.
HCO3- easily accepts proton; therefore it is a strong conjugate base making H2CO3 a weak acid.
In (D), NaOH dissociates completely into Na+ and OH- in aqueous solution. OH- is the conjugate acid formed here; it has reduced tendency to donate protons and therefore is a weak conjugate acid making NaOH a strong base.
(2)(B) is the correct answer.
Given that the H+ ion concentration[H+] of the solution is 1.0×10^(-2)M.
The value of pH for a solution helps to determine whether a given solution is acidic, basic, or neutral.
Salts can also be acidic, basic or neutral. The pH of salt solutions is also determined in the same manner.
A pH scale ranges from 1 to 14.
A solution with pH of 7 is neutral;value less than 7 is acidic and a value above 7 shows that the solution is basic.
The pH of a solution with known concentration of H+ ions is calculated as follows:
pH = -log[H+]
pH = -log[1.0× 10^(-2)]
pH = -log[10^(-2)]
pH = -(-2)
pH = 2
So, the pH of the given solution is 2; indicating that the solution is acidic.
We cannot determine whether a solution is salty from its pH value.