WHAT IS THE PH OF A NEUTRAL SOLUTION AT 25°C?

SEVEN. Pure water at 25 Celsius has equal H plus and OH minus concentrations, giving a pH of seven.

WHO DEFINED ACIDS AS PROTON DONORS?

BRONSTED LOWRY. Bronsted and Lowry defined acids as proton donors and bases as proton acceptors in 1923.

WHAT DOES A LOWER PKA INDICATE ABOUT AN ACID?

STRONGER ACID. Lower pKa means a larger Ka, so the acid dissociates more completely. That means it is a stronger acid.

WHICH OF THESE IS A STRONG ACID?

HCL. Hydrochloric acid fully dissociates in water. Acetic acid and ammonium hydroxide are weak.

WHAT IS THE CONJUGATE BASE OF SULFURIC ACID?

HSO4 MINUS. Sulfuric acid loses one proton to form hydrogen sulfate, its conjugate base. Loss of a second gives sulfate.

A BUFFER IS MOST EFFECTIVE WHEN PH EQUALS WHAT?

PKA. Buffer capacity peaks when pH equals pKa. Concentrations of weak acid and conjugate base are equal.

WHAT IS THE NORMAL PHYSIOLOGICAL BLOOD PH RANGE?

7.35 TO 7.45. Arterial blood pH is tightly regulated between 7.35 and 7.45. Outside this range causes acidosis or alkalosis.

AT THE HALF EQUIVALENCE POINT IN A TITRATION, PH EQUALS?

PKA. At the half equivalence point, equal moles of weak acid and conjugate base exist, so pH equals pKa.

ELEVATED ARTERIAL CO2 CAUSES BLOOD PH TO DO WHAT?

DECREASE. CO2 plus water shifts right to form H plus and bicarbonate. More H plus means lower pH. Respiratory acidosis.

MCATChemistry and Physics quiz

Acid-Base Chemistry

25 questions~5 min15 multiple choice · 10 fill-in

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Acid-Base Chemistry: all 25 questions

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1. What is the pH of a neutral solution at 25°C?
Seven
Pure water at 25 Celsius has equal H plus and OH minus concentrations, giving a pH of seven.
2. Who defined acids as proton donors?
Bronsted Lowry
Bronsted and Lowry defined acids as proton donors and bases as proton acceptors in 1923.
3. A substance that donates a proton is a _____ acid.
Bronsted
Bronsted acids donate H plus; Bronsted bases accept H plus. The classic acid-base definition.
4. What does a lower pKa indicate about an acid?
Stronger acid
Lower pKa means a larger Ka, so the acid dissociates more completely. That means it is a stronger acid.
5. A solution resisting pH change when acid or base is added is a _____.
Buffer
Buffers contain a weak acid and its conjugate base. They neutralize small amounts of added acid or base.
6. Which of these is a strong acid?
HCl
Hydrochloric acid fully dissociates in water. Acetic acid and ammonium hydroxide are weak.
7. A solution with a pH below seven is _____.
Acidic
Below pH seven, hydrogen ion concentration exceeds hydroxide. Above seven is basic; exactly seven is neutral.
8. What is the conjugate base of sulfuric acid?
HSO4 minus
Sulfuric acid loses one proton to form hydrogen sulfate, its conjugate base. Loss of a second gives sulfate.
9. A buffer is most effective when pH equals what?
pKa
Buffer capacity peaks when pH equals pKa. Concentrations of weak acid and conjugate base are equal.
10. An acid with more than one ionizable proton is _____.
Polyprotic
Diprotic and triprotic acids like sulfuric and phosphoric have multiple acidic protons released stepwise.
11. What is the normal physiological blood pH range?
7.35 to 7.45
Arterial blood pH is tightly regulated between 7.35 and 7.45. Outside this range causes acidosis or alkalosis.
12. The partner formed when an acid loses H plus is its _____ base.
Conjugate
Acetic acid and acetate, ammonium and ammonia are conjugate pairs. They differ by one proton.
13. Which is a Lewis acid but not a Bronsted acid?
BF3
Boron trifluoride accepts electron pairs but has no proton to donate, making it Lewis but not Bronsted.
14. A species that can ACT as both acid and base is _____.
Amphoteric
Water and amino acids are amphoteric. They donate a proton to strong bases and accept one from strong acids.
15. Which salt forms a basic solution in water?
Sodium acetate
Acetate hydrolyzes to form OH minus. Ammonium chloride is acidic; sodium chloride is neutral.
16. At the half equivalence point in a titration, pH equals?
pKa
At the half equivalence point, equal moles of weak acid and conjugate base exist, so pH equals pKa.
17. The blood's primary extracellular buffer is the _____ system.
Bicarbonate
CO2 plus water gives carbonic acid, which dissociates to H plus and bicarbonate. Controls blood pH.
18. Which indicator turns pink above pH 8.3?
Phenolphthalein
Phenolphthalein is colorless below 8.3 and pink above. Used in strong base titrations.
19. At equivalence of a weak acid + strong base titration, pH is?
Above seven
The conjugate base remaining at equivalence hydrolyzes water, producing OH minus and a basic pH.
20. What is the pH of a 0.01 molar HCl solution?
Two
HCL fully dissociates. Hydrogen ion concentration is 0.01 molar. Negative log of 0.01 equals two.
21. pH = pKa + log of a minus over ha is the _____ equation.
Henderson
Henderson Hasselbalch lets you calculate buffer pH from pKa and the ratio of conjugate base to acid.
22. Which amino acid has the lowest isoelectric point?
Aspartate
Aspartate has an acidic side chain. Its pI of about 2.8 is the lowest of the twenty standard amino acids.
23. A molecule with positive and negative charges but no net charge is a _____.
Zwitterion
At its isoelectric point, an amino acid exists as a zwitterion: protonated amine and deprotonated carboxyl.
24. Elevated arterial CO2 causes blood pH to do what?
Decrease
CO2 plus water shifts right to form H plus and bicarbonate. More H plus means lower pH. Respiratory acidosis.
25. Where moles of added base equal moles of acid is the _____ point.
Equivalence
At equivalence, the titrant has completely neutralized the analyte. The volume defines its concentration.