Which of the following substances can act as a Bronsted acid in aqueous solution? (Select all that apply.)
C3H8
NH41+
HCl
H2
H2O
H2CO3
PH3
Which of the following substances can act as a Bronsted base in aqueous solution? (Select all that apply.)
PH3
PH41+
CO32-
SO42-
H2
CH4
NH3
To determine which substances can act as a Bronsted acid or a Bronsted base in aqueous solution, we need to understand the Bronsted-Lowry definition of acids and bases.
According to the Bronsted-Lowry definition, an acid is a substance that donates a proton (H+ ion) in a chemical reaction, while a base is a substance that accepts a proton. In an aqueous solution, a substance needs to be able to donate or accept a proton in water to be considered a Bronsted acid or a Bronsted base.
Let's go through each substance and determine whether it can act as a Bronsted acid or a Bronsted base:
Bronsted acids:
1. C3H8: Propane (C3H8) is an organic compound, which means it mainly consists of carbon and hydrogen. It does not contain any acidic protons, so it cannot donate a proton. Therefore, it cannot act as a Bronsted acid.
2. NH4+ (Ammonium ion): Ammonium ion (NH4+) is a positively charged ion. It can donate a proton (H+ ion) to form NH3 (ammonia). Therefore, it can act as a Bronsted acid.
3. HCl: Hydrochloric acid (HCl) is a strong acid. It readily donates a proton (H+) in aqueous solution. Therefore, it can act as a Bronsted acid.
4. H2: Hydrogen gas (H2) does not contain any acidic protons, so it cannot donate a proton. Therefore, it cannot act as a Bronsted acid.
5. H2O: Water (H2O) can act as both an acid and a base. It can donate a proton (H+) to form the hydroxide ion (OH-) or accept a proton to form the hydronium ion (H3O+). Therefore, it can act as a Bronsted acid and a Bronsted base.
6. H2CO3: Carbonic acid (H2CO3) is a weak acid. It can donate a proton (H+) in aqueous solution. Therefore, it can act as a Bronsted acid.
7. PH3: Phosphine (PH3) is a weak acid. It can donate a proton (H+) in aqueous solution. Therefore, it can act as a Bronsted acid.
Bronsted bases:
1. PH3: Same as before, Phosphine (PH3) is able to accept a proton (H+) to form PH4+ (phosphonium ion). Therefore, it can act as a Bronsted base.
2. PH4+: Phosphonium ion (PH4+) is a positively charged ion. It can readily accept a proton (H+) to form PH3. Therefore, it can act as a Bronsted base.
3. CO3^2-: Carbonate ion (CO3^2-) is a negatively charged ion. It can accept a proton (H+) to form bicarbonate ion (HCO3-). Therefore, it can act as a Bronsted base.
4. SO4^2-: Sulfate ion (SO4^2-) is a negatively charged ion. It cannot directly accept or donate a proton. Therefore, it cannot act as a Bronsted base.
5. H2: Hydrogen gas (H2) does not readily accept a proton in aqueous solution. Therefore, it cannot act as a Bronsted base.
6. CH4: Methane (CH4) is a non-polar molecule and does not contain any basic sites to accept a proton. Therefore, it cannot act as a Bronsted base.
7. NH3: Ammonia (NH3) is a weak base. It can readily accept a proton (H+) in aqueous solution. Therefore, it can act as a Bronsted base.
Based on the explanations provided above, the substances that can act as Bronsted acids in aqueous solution are NH4+, HCl, H2O, H2CO3, and PH3.
The substances that can act as Bronsted bases in aqueous solution are PH3, PH4+, CO3^2-, and NH3.
I do not understand how to determine if the substance is an bronsted acid or base
If the substance can donate a proton, it is a Bronsted acid. If it can accept a proton, it is a Bronsted base.
examples:
Bronsted acid. HCl or NH4^+
HCl + H2O ==> H3O^+ + Cl^-
NH4^+ + H2O ==> H3O^+ + NH3
Bronsted base. NH3 or CO3^-2
NH3 + HOH ==> NH4^+ + OH^-
CO3^-2 + HOH ==> HCO3^- + OH^-