State whether each of the following aqueous solutions would be acidic, basic, or neutral. Include appropriate net-ionic equations to show why a given solution is acidic or basic.
a) NaNO3
b)KC6H5CO2
c)50:50 mixture of C6H5CO2H+KC6H5CO2
d)(CH3NH3)Cl
e)50:50 mixture of CH3NH2+(CH3NH3)Cl
f)50:50 mixture of 0.1M NaBr +0.1M HBr
How do we figure out which one is basic, acidic, or neutral from the start? How can you tell if it donates an H+ ion or not?
Im just not sure how to approach these.
Thank you.
To determine whether a solution is acidic, basic, or neutral, you need to identify the nature of the ions present in the solution. The presence of certain ions can lead to the formation of H+ or OH- ions, which determine the pH.
a) NaNO3: Sodium nitrate (NaNO3) is composed of Na+ and NO3- ions. Neither of these ions react with water to produce H+ or OH- ions. Therefore, the solution will be neutral.
b) KC6H5CO2: Potassium benzoate (KC6H5CO2) is composed of K+ and C6H5CO2- ions. When the benzoate ion (C6H5CO2-) reacts with water, it does not produce H+ or OH- ions. Consequently, the solution will be neutral.
c) Mixture of C6H5CO2H + KC6H5CO2: Benzoic acid (C6H5CO2H) is a weak acid, which means it partially dissociates in water. The mixture of benzoic acid and its salt, potassium benzoate, will produce benzoate ions (C6H5CO2-) and a few H+ ions from the benzoic acid. This results in the solution being slightly acidic.
The net-ionic equation for the reaction with water:
C6H5CO2H + H2O ⇌ C6H5CO2- + H3O+
d) (CH3NH3)Cl: Methylammonium chloride [(CH3NH3)Cl] contains a positively charged methylammonium ion (CH3NH3+) and a chloride ion (Cl-). The methylammonium ion does not react with water to produce H+ or OH- ions. Hence, the solution will be neutral.
e) Mixture of CH3NH2 + (CH3NH3)Cl: Methylamine (CH3NH2) is a weak base that partially dissociates in water. The mixture of methylamine and its salt, methylammonium chloride, will produce methylammonium ions (CH3NH3+) and a few OH- ions from the methylamine. As a result, the solution will be slightly basic.
The net-ionic equation for the reaction with water:
CH3NH2 + H2O ⇌ CH3NH3+ + OH-
f) Mixture of 0.1M NaBr + 0.1M HBr: Sodium bromide (NaBr) is the salt of a strong acid (HBr) and a strong base (NaOH). Therefore, it dissociates completely into Na+ and Br- ions, which will not react further with water. Additionally, HBr is a strong acid, meaning it also dissociates completely into H+ and Br- ions. Hence, the solution will be acidic due to the presence of H+ ions from HBr.
The net-ionic equation for the dissociation of HBr:
HBr + H2O → H3O+ + Br-
By analyzing the nature of the ions present in each compound and their reactions with water, you can determine whether the solution will be acidic, basic, or neutral.