Chemistry: Acids and Bases

Name 6 strong acids

1. HI 2. HBr 3. HCl 4. HClO4 5. H2SO4 6. HNO3

Calculate the pH of a 1.00M solution of acetic acid.

1.8x10^-5 = x^2 x = 0.0042 M pH = -log(4.2x10^-3) pH = 2.38

Amphoteric Vs. Amphiprotic

A substance which can act as either an acid or a base is described as being amphoteric. Note: You might also come across the term amphiprotic in this context. The two words are related and easily confused. An amphiprotic substance is one which can both donate hydrogen ions (protons) and also accept them.

Give an example of a Arrhenius Acid and Arrhenius Base.

Arrhenius Acids -compounds that produce H+ ions HCL <-> H+ + Cl- Arrhenius Bases -compounds that produce OH- ions NaOH <-> Na+ and OH-

How does the principles of induction affect the acidity of a molecule?

Electronegative elements positioned near an acidic proton increase acid strength by pulling electron density out of the bond holding the acidic proton. This weakens proton bonding and facilitates dissociation.

TRUE OR FALSE A pH scale begins and ends at 0 to 14.

FALSE A pH scale can be negative (below 0) or greater than 14. This would imply a very high concentration of strong acid or base.

TRUE OR FALSE The greater the Ka value (acid dissociation constant) of an acid, the weaker the acid, and consequently, the less it will dissociate.

FALSE The smaller the Ka, the weaker the acid, and consequently, the less it will dissociate. Ka = ([H3O+][A-])/[HA]

Draw an example reaction of a Bronsted-Lowry acid/base reaction. Indicate which molecule is the Bronsted-Lowry acid and which is the Bronsted-Lowry base. Indicate the conjugate acid and conjugate base

H20 + HCl -> H3O+ + Cl- H2O = base (proton acceptor) HCl = acid (proton donor) H3O+ = conjugate acid Cl- = conjugate base

What is the pH of a solution with [HClO4] = 10M?

HClO4 is a strong acid, thus, it will completely dissociate. Therefore, [H+] = 10M pH = -log(10) = -1

How do you recognize a strong acid based on its given equilibrium constant, Ka?

If the Ka >>>1, then the acid can be considered a strong acid.

Write the equilibrium equation for the following reaction: H2O + HCl -> H30+ + Cl-

Ka = ([H3O+][Cl-])/[HCl])

Calculate the concentration of H3O+ in a 2.0 M aqueous solution of acetic acid, CH3OOH. Ka = 1.8x10^-5

Ka = [x^2]/[2.0 - x] (1.8x10^05) = [x^2]/[2.0 - x] x = 6x10^-3 M

What is the relationship between the Ka and Kb for an acid-base conjugate pair?

Ka*Kb = Kw = 1x10^-14

Calculate the pH of a 0.500 M solution of NH3.

Kb = ([OH-][NH4]/[NH3]) 1.8x10^-5 = x^2 x = 0.0030 M = [OH-] pOH = -log (3x10^-3) = 2.52 pH = 14 - pOH = 11.5

Consider the autoionization of water: 2 H2O <-> H3O+ + OH- What is the equilibrium constant (Kw) calculated to be?

Kw = [H3O+][OH-] Kw = (1.0x10^-7)(1.0x10^-7) Kw = 1.0x10^-14 M

Define Lewis acid and Lewis base.

Lewis acid = electron pair acceptor Lewis base = electron pair donor

Practice Leah4sci MCAT math

Practice Leah4sci MCAT math

TRUE OR FALSE The product of the concentrations of the hydrogen ion and the hydroxide ion must always equal 10^-14 for acidic and basic aqueous solutions.

TRUE

TRUE OR FALSE: The stronger the acid, the weaker its conjugate base?

TRUE

Based on the three definitions of acids/bases, which is the most inclusive?

The Lewis definition is the most inclusive: every Arrhenius acid is also a Bronsted-Lowry acid and likewise for bases.

What does it mean for the value of Ka to be greater than 1?

The forward reaction is favorable

What is the relationship between Kb and basicity?

The higher the value of Kb, the stronger the base.

How does pKa relate to acid strength?

The lower the pKa of a weak acid, the stronger it's acidity.

What does it mean for a molecule to be amphoteric?

The molecule can function as an acid or a base.

How much 0.1 M NaOh solution is needed to neutralize 40 mL of a 0.3 M HCl solution?

Vb = (a*[A]*Va)/(b*[B]) Vb = 120 mL

Orange Juice has a pH of 3.5, What is its [H+]?

[H+] = 10^-3.5 => 10^.5-4 => 10^-.5 * 10^-4 => approx. 3.2x10^-4 M

Given the following sets of data, determine the [H30+], pOH, and [OH-] concentrations of: a) Solution with a pH = 4 b) Soln w/ pH = 8.81

a) [H3O+] = 10^-4 pOH = 10 [OH-] = 10^-10 b) [H3O+] = 1.55x10^-9 pOH = 5.19 [OH-] = 6.46x10^-6

a) If [H+] = 10^-2, then pH =? b) If the Kb = 1.0x10^-12, then pKb =? c) If Ka = 1.8x10^-5, then pKa =?

a) 2 b) 12 c) Use: -log (nx10^-m) => m - log(n) pKa = -log (1.8x10^-5) = 5 - log(1.8) = 5 - 0.18 => 4.82

Differentiate between the three definitions for acids and bases: a) Arrhenius acid/base b) Bronsted Lowry acid/base c) Lewis acid/base

a) Arrhenius acid/base -acids dissociate to form an excess of H+ while bases dissociate to form an excess of OH-. b) Bronsted Lowry acid/base -acids donate H+ while bases accepts them. c) Lewis acid/base -acids are electron pair acceptors while bases are electron pair donors

Based off the three definitions of acids/bases, identify which type of acid/base can the following chemical groups can be? a) H2O b) NH3 c) HNO3 d) HCl e) BF3 f) F- g) NaOH

a) H2O b) NH3 c) HNO3 d) HCl e) BF3 f) F- g) NaOH

Describe how a solution is affected within the following reactions: a) Strong Acid + Strong Base b) Strong Acid + Weak Base c) Weak acid + Strong Base d) Weak Acid + Weak Base

a) Strong Acid + Strong Base => Neutralization occurs so that the resulting solution is neutral (pH = 7). b) Strong Acid + Weak Base => pH of a solution will fall below 7 to produce a slightly acidic solution. c) Weak Acid + Strong Base => pH will rise above 7. d) Weak Acid + Weak Base => Depends on the relative amounts of the reactants. If the Ka of the weak acid is greater than Kb of weak base, then the solution will be acid because in equilibrium, there will be a greater concentration of hydronium ions than hydroxide ions.

The water dissociation constant, Kw = 10^-14 at 298K. Which of the following changes would affect Kw: a) Temperature b) Concentration c) Pressure d) Volume

a) Temperature --> YES b) Concentration --> NO c) Pressure --> NO d) Volume --> NO

Explain how a water molecule exhibits both the properties of being amphoteric and amphiprotic

a) When water reacts with a base, it behaves as a acid: H20 + B- <--> HB + OH- *Loses a proton* b) When water reacts with an acid, it behaves as a base: HA + H20 <--> H3O+ + A- *Gains a proton*

Complete the sentence: a) Strong acids/bases produce ____conjugate acids/bases. b) Weak acids/bases produce _____ conjugate acids/bases.

a) weak b) weak

To determine just how much base (B) to add to an acidic solution (or how much acid (A) to add to a basic solution) to cause neutralization, what formula can be used?

a*[A]*Va = b*[B]*Vb

List some strong bases

lithium hydroxide sodium hydroxide potassium hydroxide rubidium hydroxide barium hydroxide calcium hydroxide strontium hydroxide NaOH Li2O NaNH2

What is the relationship between pKa and pKb?

pKa + pKb = 14