Proton Transfer Reactions (DP IB Chemistry)
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1/89Define Brønsted-Lowry acid?
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Define Brønsted-Lowry acid?
A Brønsted-Lowry acid is a species that gives away a proton (H+).
Define Brønsted-Lowry base?
A Brønsted-Lowry base is a species that accepts a proton (H+).
In the following reaction, which species is acting as a Brønsted-Lowry acid?
HCl (aq) + H2O (l) → Cl- (aq) + H3O+ (aq)
In the following reaction, HCl (aq) is acting as a Brønsted-Lowry acid.
HCl (aq) + H2O (l) → Cl- (aq) + H3O+ (aq)
In the following reaction, which species is acting as a Brønsted-Lowry base?
HCl (aq) + H2O (l) → Cl- (aq) + H3O+ (aq)
In the following reaction, H2O (l) is acting as a Brønsted-Lowry base.
HCl (aq) + H2O (l) → Cl- (aq) + H3O+ (aq)
True or False?
All bases are alkalis.
False.
Not all bases are alkalis.
True or False?
An alkali is a soluble base.
True.
An alkali is a soluble base.
In the following reaction, which species is acting as a Brønsted-Lowry acid?
HCl (g) + NH3 (g) → NH4Cl (s)
In the following reaction, HCl (l) is acting as a Brønsted-Lowry acid.
HCl (g) + NH3 (g) → NH4Cl (s)
In the following reaction, which species is acting as a Brønsted-Lowry base?
HCl (g) + NH3 (g) ⇌ NH4Cl (s)
In the following reaction, NH3 (g) is acting as a Brønsted-Lowry base.
HCl (g) + NH3 (g) ⇌ NH4Cl (s)
In the following reaction, what species is acting as a Brønsted-Lowry base?
H2PO4− (aq) + H2O (l) → HPO42− (aq) + H3O+ (aq)
In the following reaction, H2O (l) is acting as a Brønsted-Lowry base.
H2PO4− (aq) + H2O (l) → HPO42− (aq) + H3O+ (aq)
In the following reaction, what species is acting as a Brønsted-Lowry acid?
H2PO4− (aq) + H2O (l) → HPO42− (aq) + H3O+ (aq)
In the following reaction, H2PO4− (aq) is acting as a Brønsted-Lowry acid.
H2PO4− (aq) + H2O (l) → HPO42− (aq) + H3O+ (aq)
True or False?
A proton in aqueous solution can be represented as H+ (aq) only.
False.
A proton in aqueous solution can be represented as both H+ (aq) and H3O+ (aq).
What is meant by conjugate acid-base pair?
A conjugate acid-base pair is two species that are different from each other by a H+ ion.
In the following reaction, what is the acid and conjugate base pair?
H2CO3 (aq) + OH- (aq) ⇌ HCO3- (aq) + H2O (l)
In the following reaction, the acid and conjugate base pair is H2CO3 (aq) and HCO3- .
H2CO3 (aq) + OH- (aq) ⇌ HCO3- (aq) + H2O (l)
In the following reaction, what is the base and conjugate acid pair?
H2PO4− (aq) + CN- (aq) ⇌ HCN (aq) + HPO42− (aq)
In the following reaction, the base and conjugate acid pair is CN- (aq) and HCN (aq) .
H2PO4− (aq) + CN- (aq) ⇌ HCN (aq) + HPO42− (aq)
In the following reaction, what is the acid and conjugate base pair?
HSO4- (aq) + OH- (aq) ⇌ SO4- (aq) + H2O (l)
In the following reaction, the acid and conjugate base pair is HSO4- (aq) and SO4- (aq).
HSO4- (aq) + OH- (aq) ⇌ SO4- (aq) + H2O (l)
In the following reaction, what is the acid and conjugate base pair?
HCO3- (aq) + H2O (l) ⇌ CO32- (aq) + H3O+ (aq)
In the following reaction, the acid and conjugate base pair is HCO3- (aq) and CO32- (aq).
HCO3- (aq) + H2O (l) ⇌ CO32- (aq) + H3O+ (aq)
True or False?
In the following reaction the acid on the left hand side has a conjugate acid on the right hand side.
H2SO4 + HNO3 ⇋ H2NO3+ + HSO4-
False.
In the following reaction the acid on the left hand side has a conjugate base on the right hand side.
H2SO4 + HNO3 ⇋ H2NO3+ + HSO4-
What is the conjugate acid in the following reaction?
CH3COOH + HCl ⇌ CH3COOH2+ + Cl-
The conjugate acid in the reaction is CH3COOH2+.
CH3COOH + HCl ⇌ CH3COOH2+ + Cl-
What is the conjugate base of NH4+?
The conjugate base of NH4+ is NH3.
True or False?
The conjugate base of a strong acid is a weak base.
True.
The conjugate base of a strong acid is a weak base.
What is the relationship between the strength of an acid and its conjugate base?
The relationship between the strength of an acid and its conjugate base is:
The stronger the acid, the weaker its conjugate base.
Define amphiprotic.
Amphiprotic is a term describing species that can act both as proton donors and acceptors.
True or False?
Water is an example of an amphiprotic species.
True.
Water is an example of an amphiprotic species.
What is an amphoteric compound?
An amphoteric compound has both basic and acidic character.
True or False?
All amphiprotic substances are amphoteric.
True.
All amphiprotic substances are amphoteric.
True or False?
All amphoteric substances are amphiprotic.
False.
Not all amphoteric substances are amphiprotic.
For example, aluminium oxide is amphoteric but not amphiprotic.
True or False.
Amphiprotic substances can only accept protons.
False.
Amphiprotic substances can both accept or donate protons.
In the following equation, is Al2O3 acting as an acid or base?
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) → 2NaAl(OH)4 (aq)
In the following equation is Al2O3 is acting as an acid.
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) → 2NaAl(OH)4 (aq)
True or False.
HCO3− is amphiprotic.
True.
HCO3− is amphiprotic.
Define pH.
pH is the negative logarithm of the hydrogen ion concentration in mol dm-3
pH = -log[H+]
What does the pH scale measure?
The pH scale measures how acidic or basic a substance is.
True or False?
The pH scale is linear.
False.
The pH scale is logarithmic.
What is the pH range for acidic solutions?
The pH range for acidic solutions is 0-6 .
What is the pH range for alkaline solutions?
The pH range for alkaline solutions is 8-14.
What is the most accurate way of measuring pH?
The most accurate way of measuring pH is using a pH meter.
What is the pH of a neutral solution at 298K?
The pH of a neutral solution at 298K is 7.
How does pH change as [H+] increases?
As [H+] increases, pH decreases.
True or False?
A solution with pH 4 is 10 times more acidic than a solution with pH 5.
True.
A solution with pH 4 is 10 times more acidic than a solution with pH 5.
What is the pH of a solution that has an H+ concentration of 0.001 mol dm-3 at 298 K?
The pH of a solution that has an H+ concentration of 0.001 mol dm-3 at 298 Kis pH 3.
In alkaline solutions which ions are in a greater concentration than H+ ions?
In alkaline solutions OH- ions are in a greater concentration than H+ ions.
True or False?
Using universal indicator is a more accurate method is to measure the pH of a substance than a using a pH meter.
False.
Using universal indicator is a less accurate method is to measure the pH of a substance than a using a pH meter.
Calculate the pH of HCl with a concentration of 0.43 mol dm-3.
pH = -log[H+]
The pH of HCl with a concentration of 0.43 mol dm-3 is 0.37.
pH = -log[0.43]
pH = 0.37
Write the equation for the equilibrium established in water.
An equation for the equilibrium established in water is:
H2O (l) ⇌ H+ (aq) + OH- (aq).
State the equation for the ion product of water.
The equation for the ion product of water is:
Kw = [H+][OH-]
True or False?
The value of Kw remains constant at all temperatures.
False.
The value of Kw changes with temperature.
How does increasing temperature affect Kw?
As temperature increases, Kw increases.
What is the relationship between [H+] and [OH-] in pure water at 298 K?
In pure water at 298K, [H+] = [OH-].
True or False?
In acidic solutions, [H+] > [OH-].
True.
In acidic solutions, [H+] > [OH-].
True or False?
In alkaline solutions, [H+] < [OH-].
True.
In alkaline solutions, [H+] < [OH-].
How does the pH of water change with increasing temperature?
As temperature increases, the pH of water decreases.
Is the ionisation of water exothermic or endothermic?
The ionisation of water is endothermic.
A solution of sodium hydroxide, NaOH (aq) has a concentration of 1.0 × 10−4 mol dm−3 ?
(Kw = 1.0 × 10−14 at 298 K)
What is the pH of the solution?
The pH of a solution of sodium hydroxide, NaOH (aq) of concentration 1.0 × 10−4 mol dm−3 is 10.
Kw = [H+] [OH-]
Rearranging gives [H+] = Kw ÷ [OH-]
[H+] = (1.0 × 10−14) ÷ (1.0 × 10−4) = 1.0 × 10−10 mol dm−3
pH = – log10[1.0 × 10−10 (aq)]
So the pH = 10
Why is [H2O (l)] not included in the expression for Kw?
[H2O (l)] not included in the expression for Kw a s the concentration of water molecules remains constant.
Define strong acid.
A strong acid is an acid that dissociates almost completely in aqueous solutions.
Define weak acid.
A weak acid is an acid that partially (or incompletely) dissociates in aqueous solutions.
True or False?
Weak acids are proton donors and their solutions are poor conductors.
True.
Weak acids are proton donors and their solutions are poor conductors.
Define strong base.
A strong base is a base that dissociates almost completely in aqueous solutions.
True or False?
HCl, HBr, HI, HNO3 and H2SO4 are all strong acids.
True.
HCl, HBr, HI, HNO3 and H2SO4 are all strong acids.
Give an example of a strong base.
Examples of strong bases include Group 1 hydroxides (e.g. NaOH, KOH)
Which is a stronger acid, HBr or HI?
HI is a stronger acid than HBr.
This is because the HI bond is a longer bond than HBr and is weaker. Therefore H+ ions are more easily released.
Do strong or weak acids conduct electricity better?
Strong acids conduct electricity better than weak acids.
A stronger acid has a higher concentration of H+ so it conducts electricity better.
Which acid has a higher pH?
CH3CH2COOH or HNO3
CH3CH2COOH has a higher pH than HNO3.
Why do strong acids react more vigorously than weak acids?
Strong acids react more vigorously because the concentration of H+ is greater in strong acids compared to weak acids.
Write an equation for the ionisation of ethanoic acid.
The equation for the ionisation of ethanoic acid is:
CH3COOH (aq)
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CH3COO- (aq) + H+ (aq) Why are stronger acids better at conducting electricity than weak acids?
A strong acid has a higher concentration of H+ ions so it conducts electricity better than a weak acid.
Why are weak acids less acidic than strong acids?
Weak acids are less acidic than strong acids as they contain fewer H+ in solution. This is because they only partially ionise.
Give an example of a weak base.
Weak bases include:
NH3
Amines
Some transition metal hydroxides
True or False?
In general, strong acids produce strong conjugate bases and weak acids produce weak conjugate bases.
False.
In general, strong acids produce weak conjugate bases and weak acids produce strong conjugate bases.
Write the ionic equation to show how a base accepts hydrogen ions.
The ionic equation to show how a base accepts hydrogen ions is:
OH– (aq) + H+ (aq) ⇌ H2O (l)
HNO3 dissociates to form H+ and NO3- ions.
Is the NO3- ion a strong or weak conjugate base?
HNO3 dissociates to form H+ and NO3- ions.
The NO3- ion is a weak conjugate base.
True or False?
A solution of 10 mol dm-3 HCN is a concentrated weak acid.
True.
A solution of 10 mol dm-3 HCN is a concentrated weak acid.
Define neutralisation reaction.
A neutralisation reaction is one in which an acid and a base/alkali react together to form water and a salt
What type of salt is produced if an alkali is added to sulfuric acid?
A sulfate salt is produced when sulfuric acid is reacted with an alkali.
What type of salt is produced if an alkali is added to nitric acid?
A nitrate salt is produced when nitric acid is reacted with an alkali.
What type of salt is produced if an alkali is added to hydrochloric acid?
A chloride salt is produced when hydrochloric acid is reacted with an alkali.
What acid is used to make ethanoate salts?
Ethanoic acid is used to make ethanoate salts.
State the general equation for the reaction between an acid and a metal hydroxide.
The general equation for the reaction between an acid and a metal hydroxide is:
acid + metal hydroxide → salt + water
Write the symbol equation for the reaction between hydrochloric acid + potassium hydrogencarbonate.
The equation for the reaction between hydrochloric acid + potassium hydrogencarbonate is:
HCl (aq) + KHCO3 (s) → KCl (aq) + H2O (l) + CO2 (g)
Write the equation for the reaction between nitric acid + copper carbonate .
The equation for the reaction between nitric acid + copper carbonate is:
2HNO3 (aq) + CuCO3 (s) → Cu(NO3)2 (aq) + H2O (l) + CO2 (g)
Write the equation for the reaction between sulfuric acid + barium hydroxide.
The equation for the reaction between sulfuric acid + barium hydroxide is:
H2SO4 (aq) + Ba(OH)2 (aq) → BaSO4 (s) + 2H2O (l)
What salt is formed when sulfuric acid reacts with ammonia?
Ammonium sulfate is formed when sulfuric acid reacts with ammonia.
What base could be used to form copper(II) chloride?
Bases that could be used to form copper(II) chloride are copper(II) oxide, copper(II) hydroxide, copper(II) carbonate.
Name the piece of equipment that can be used to measure the pH during a titration to plot a curve.
During a titration, a pH meter can be used and a pH curve plotted.
What is point X called?
X is the equivalence or stoichiometric point.
What is the pH at the equivalence point of a titration between HCl and NaOH?
The pH at the equivalence point of a titration between HCl and NaOH is 7.
What four pieces of information can be obtained from a pH curve?
From a pH curve, you can determine:
The initial pH of the acid
The pH at the equivalence point
The volume of base at the equivalence point
The range of pH at the vertical section of the curve
What is the pH at the start of the titration?
The pH at the start of the titration is pH 3.
What is the pH at equivalence point?
The pH at equivalence point is pH 8.
What volume of NaOH (aq), in cm3, was added to reach equivalence point?
The volume of NaOH (aq) that was added to reach the equivalence point is 30 cm3.
