Acid - Base Questions
1. Name each of the following and indicate whether it is an acid or a base.
HBr (aq)=A
hydrobromic acid
Mg(OH)2=B
HClO3 (aq)=A
H2S (aq) =A
magnesium hydroxide chloric acid
hydrosulfuric acid
LiOH (aq)=B H2SO3(aq)=A
lithium hydroxide sulfurous acid
CH3CH2COOH (aq)=A
NH4OH (aq)=B
propanoic acid
ammonium hydroxide
2. Which of the following would be a property of citric acid?
a) It would react with fats and oils to produce a soap and therefore a solution of it would feel
slippery.
b) It would react with calcium hydroxide to form calcium citrate and water.
c) It would react with zinc to produce zinc citrate and hydrogen gas
d) A dilute solution of citric acid would have a bitter taste.
e) It would cause an acid base indicator to be the same colour as an ammonia solution.
f) It would produce a solution which has a pH less than 7
3. ClO2- ions are called chlorite ions
Why is the name of HClO2 (aq) chlorous acid not hydrochlorous acid?
The prefix hydro is not used with acids containing a polyatomic ion
Why is the name of HClO2 (aq) chlorous acid not chloric acid?
ClO2- is the chlorite, and ite ions are named ous acids
Finish the following reaction of HClO2 and H2O
ClO2+
H3 O+
-------------------------------4. Which of the following of molecules do you recognize as acidic and why?
HClO2
H
H–C–O -H
H
+
H2O
------->
H
H–C=O
H
H
H–C–O–C-H
H
O
H–C–O–H
H
Why? It contains a COOH group that can donate a hydrogen(a proton) to another substance
like water.
5. Lithium hydroxide is a strong base. Carbonic acid is a weak acid.
Lithium carbonate (Li2CO3 ) is a “salt used in the treatment of manic depressant disorders.
What type of “salt” is lithium carbonate and why? Acidic, Basic,Neutral
Lithium carbonate is a basic salt because it is composed of a strong base and a weak acid.
When dissolved in water it will create a solution with a greater concentration of OH- ions than
H3O+ ions
Strong Acids include HCl, HBr, HI, HNO3, H2SO4, HClO4
Strong Bases include LiOH , NaOH, KOH, RbOH, CsOH, Ba(OH)2
6. Finish the following reaction
___3__ KOH (aq) + ______ H3PO4 (aq) -------> K3PO4(aq) + 3H2O(l)
Strong Base
weak acid
basic salt
What type of “salt” is produced from the above reaction and why?Acidic Basic Neutral
Potassium phoshphate is also a basic salt because it is composed of a strong base and a weak
acid. When dissolved in water it will create a solution with a greater concentration of OH- ions
than H3O+ ions
7. A student spills 20 mL of 2.0 M HCl (aq). Will the student need more than 20 ml of .75 M NaOH,
less than 20 ml of .75 M NaOH (aq) or 20 ml of .75 M NaOH (aq) to neutralize the acid spilled?
Give a reason for your answer.
The base at .75 M is less concentrated than the 2.0 M HCl therefore more of than 20 mL
of the less concentrated NaOH will be needed to neutralize the 20 ml of the more
concentrated HCl
8. How can you determine the concentration of a 25.0 ml of a Benzoic acid solution given
a supply of .75 M NaOH (aq) and bromothymol blue? Please be specific
a) Add 5.0 mL of the Benzoic acid solution to a concical flask
b) Add 5 drops of the bromothymol blue indicator.
c) Put the .75 M NaOH(aq) into a burette. Record the initial volume of the NaOH.
d) Add the .75 M NaOH(aq) into the benzoic acid until it turns blue.
e) Record the final volume of NaOH in the burette.
f) Repeat steps a through e.
f) Use the following formula: Mbenzoic acid = MNaOH VNaOH
Vbenzoic acid
9. What is the concentration of the 25.0 ml Benzoic acid solution if it can be neutralized by
5.2 ml of a .01 M NaOH solution?
Mbenzoic acid = MNaOH VNaOH = .01 M ( 5.2 mL ) = .002 M Benzoic acid
Vbenzoic acid
(25.0 mL)
10. Red wine has a concentration of hydronium ion ( H+ or H3O+ ) concentration of 7.0 x 10-2 M.
a) What is the pH of red wine? pH = -log (7.0 x 10-2) = 1.15
7.0x10-2 log - = 1.15
b) What is the pOH of the red wine? 14 – 1.15 = 12.85
c) What is the OH- ion concentration of the red wine? 10-12.85 = 1.43 x10-13 M
10x -12.85 = 1.43 x10-13 or -12.85 10x = 1.43 x10-13
d) Is red wine acidic or basic? Acid
11. Household bleach has a pH of 12.6.
a) What is the H3O+ ion concentration of the bleach? 10-12.6 = 2.51 x10-13 M
b) What is the pOH of the bleach? 14 – 12.6 = 1.4
c) What is the OH- ion concentration of the bleach? 10-1.4= 3.98 x10 -2 M
d) Is the bleach acidic or basic Basic the OH- concentration is higher than the H3O+
12. Identify the acids and bases in each of the following reactions.
a)
H2PO4- (aq)
Base 1
+
b)
H3PO4 (aq)
Acid 1
+
H3O+(aq)
Acid 2
OHBase 2
------>
------>
H2O (l)
Base 2
H2O (l)
Acid 2
+ H3PO4 (aq)
Acid 1
+
H2PO4- (aq)
Base 1
c)
The H3PO4 (aq) and the NaH2PO4(aq) can be used as an acid base buffer. What is an acid
base buffer? Explain how acid base buffers work. Acid base buffers are composed of weak
acids and their conjugate bases ( the acid has one more hydrogen, the base has one less hydrogen)
The acid in the buffer can neutralize base added to the system keeping the pH stable. The
conjugate base in the buffer can neutralize acid added to the system keeping the pH stable
13. HF has a Ka of 6.8 x 10-4 and HCN has a Ka of 4.9 x 10-10
a) A 1.0 M HF solution will create more H3O+(aq) ions than a 1.0 M HCN solution.
b) A 1.0 M HF solution will create less H3O+(aq) ions than a 1.0 M HCN solution.
c) A 1.0 M HF solution will create the same number of H3O+(aq) ions as 1.0 M HCN solution.
Give a reason for your answer.
The Ka of the HF is larger than the Ka of the HCN indicating that HF will produce more H3O+ ions
than the HCN. The HF is a stronger acid. The HF more readily ionizes water molecules.
14. Given the following data from a back titration lab calculate the volume of .50 M HCl (aq)
which can be neutralized by a Rolaids Tablet.
Mass of the tablet = 1.11 g
Mass of “1/4” tablet used to neutralize the .50 M HCl (aq) = .23 g
Volume of .50 M HCl (aq) added to the tablet = 25.0 ml
Initial volume of .50 M NaOH (aq) = 3.3 ml
Final volume of .50 M NaOH (aq) = 16.3 ml
Volume of NaOH (aq)
1. Volume of acid neutralized by the .23 g of tablet = 25.0 mL – (16.3mL -3.3mL) = 15.0 mL
2.
1.11 g = x
.23 g
15.0 mL
x = 72 mL of the .50 M HCl(aq)
15. How many times more hydronium ions (H3O+) ions does rain at a pH of 4.1 have when compared
to rain at a pH of 5.6?
10-4.1 = 7.94 x10-5 M = 31.76 times more hydronium ions at pH 4.1 compared to pH 5.6
10-5.6
2.51x10-6 M
Please study the pH vs volume of either acid or base added to a base or acid solution, the pH
titration lab, the sour candy lab, and the shaws, tums lab.