Acid Base Equilibria Flashcards
What is the pH scale used for?
The pH scale is used to measure the acidity or alkalinity of a solution.
Who developed the pH scale?
The pH scale was developed by biochemist Søren Sørensen.
True or False: A lower pH value indicates a more alkaline solution.
True: A lower pH value indicates a more acidic solution.
What is the pH range of neutral solutions?
The pH range of neutral solutions is 7.
Fill in the blank: In brewing, the ideal pH for beer fermentation is typically between ___ and ___.
4.0 and 5.0.
What happens to yeast activity when the pH is too low during brewing?
Yeast activity can be inhibited, leading to fermentation problems.
In winemaking, what role do acids play?
Acids contribute to the flavor, stability, and preservation of the wine.
Multiple choice: Which acid is commonly found in milk?
Lactic acid.
What is the effect of high acidity on the taste of beer?
High acidity can result in a sour taste.
True or False: All acids are harmful in brewing.
False: Some acids are necessary for flavor and preservation.
What is the primary acid found in grapes used for winemaking?
Tartaric acid.
Fill in the blank: The process of converting sugars to alcohol by yeast is called ___.
fermentation.
What is the ideal pH for milk fermentation?
Around 6.5 to 6.8.
Multiple choice: Which of the following is NOT a common type of acid in brewing? A) Acetic acid B) Citric acid C) Nitric acid
C) Nitric acid.
What is the significance of buffering capacity in brewing?
It helps maintain a stable pH during fermentation.
True or False: The presence of acids in beer can enhance its aroma.
True.
What is the role of lactic acid bacteria in brewing?
They can produce lactic acid, contributing to sour beer flavors.
Fill in the blank: The addition of ___ can lower the pH of the brewing water.
acidic salts.
What effect does temperature have on the fermentation process?
Temperature affects yeast activity and the rate of fermentation.
Multiple choice: Which of the following is a byproduct of fermentation? A) Carbon dioxide B) Oxygen C) Nitrogen
A) Carbon dioxide.
What is the primary goal of acid management in brewing?
To achieve the desired flavor profile and stability of the beverage.
True or False: The acidity of milk increases during fermentation.
True.
What is the impact of adding citric acid to beer?
It can enhance the beer’s freshness and flavor.
Fill in the blank: The pH of most beers is between ___ and ___.
4.0 and 5.0.
What is the role of sulfuric acid in brewing?
It is used to adjust the pH of brewing water.
What type of acid is primarily responsible for the sour taste in sour beers?
Lactic acid.
What identifies acids?
Sour taste, color changes of indicators, reactions with metal oxides, hydroxides, carbonates, and metals
Acids produce ionic compounds called salts when they react.
What identifies bases?
Slimy feel, effect on indicators, ability to neutralize acids
If a base dissolves in water, it is called an alkali.
What are the three main types of acid reactions?
- With bases (metal oxides or hydroxides)
- With metal carbonates
- With reactive metals
Fill in the blank: If a base dissolves in water, it is called an _______.
alkali
What is produced when acids react with metals?
Salts
Name an example of an acid reacting with a base.
H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)
This reaction forms sodium sulfate and water.
Name an example of an acid reacting with a metal carbonate.
2CH3COOH(aq) + K2CO3(aq) → 2CH3COOK(aq) + H2O(l) + CO2(g)
This reaction produces potassium ethanoate, water, and carbon dioxide.
Who proposed that all acids contain hydrogen?
Davy (1816)
Who defined acids as substances containing hydrogen which could be replaced by a metal?
Liebig (1838)
True or False: Arrhenius (1887) thought of acids as producing hydroxide ions.
True
What did Lavoisier propose about acids?
He proposed that all acids contain oxygen.
What is the result of the reaction between nitric acid and zinc?
ZnCl2(aq) + H2(g)
This reaction produces zinc chloride and hydrogen gas.
What is an ionic compound produced from acid reactions?
Salts
Fill in the blank: The German word for oxygen is _______.
Sauerstoff
What is produced when acids react with water?
Hydrogen ions (H+)
What does the Lewis theory describe acids as?
Electron pair acceptors
The Lewis theory expands the definition of acids beyond hydrogen-containing species.
What do Lewis bases act as in the formation of dative covalent bonds?
Electron pair donors
This concept is crucial for understanding acid-base reactions in the Lewis framework.
Provide an example of a Lewis acid.
Boron trifluoride (BF₃)
BF₃ acts as an electron pair acceptor in reactions.
Provide an example of a Lewis base.
Ammonia (NH₃)
NH₃ donates an electron pair to form a bond with a Lewis acid.
True or False: Boron trifluoride can be classified as a Lowry-Bronsted acid.
False
Boron trifluoride contains no hydrogen and cannot donate protons.
Complete the statement: All Lowry-Bronsted acids are also _______.
Lewis acids
This indicates that the Lewis definition encompasses a broader range of substances.
What ion can only form bonds by accepting an electron pair?
H⁺ ion
The H⁺ ion acts as an acid in the Lewis sense but requires electron pairs for bonding.
Identify the conjugate pairs in the reaction: HNO₃ + OH⁻.
HNO₃ and NO₃⁻, OH⁻ and H₂O
Conjugate acid-base pairs consist of species that differ by a proton.
What are positive ions called?
Cations.
Cations move towards the cathode (negative electrode)
What are negative ions called?
Anions.
Anions move towards the positive anode
Who developed the Lowry-Brønsted theory of acidity?
Thomas Lowry and Johannes Bronsted.
They independently developed this theory
According to the Lowry-Brønsted theory, what defines an acid?
A substance that can donate a proton (an H ion).
According to the Lowry-Brønsted theory, what defines a base?
A substance that can accept a proton.
What does hydrogen chloride (HCl) act as when it donates a proton to ammonia (NH3)?
An acid.
What does ammonia (NH3) act as when it accepts a proton from hydrogen chloride (HCl)?
A base.
What are acids and bases said to do in reactions?
React in pairs: one acid and one base.
What is the conjugate base of HCl?
Cl- ion.
What is the conjugate acid of ammonia (NH3)?
Ammonium ion (NH4+).
What happens to HCl after it donates a proton?
It forms the Cl- ion.
What is the relationship between conjugate acids and bases?
Conjugate acid: One can donate a proton to return to its original form
Conjugate base: happens when an acid donates its proton (H+)
What does HCl do when it donates a proton to water?
Forms a hydroxonium ion (H3O+).
What is the term for the ion formed when water accepts a proton?
Hydronium ion (H3O+).
Is HCl a better acid than NH3?
Yes.
What is the oxonium ion also known as?
Hydronium ion.
Fill in the blank: In the reaction HCl + NH3, HCl acts as a _____ and NH3 acts as a _____.
Acid, base.
Fill in the blank: Water can act as a _____ when it accepts a proton.
Base.
What are acids and bases in the context of proton competition?
Acid and base reactions can be thought of as competitions for protons, with the better base ‘winning’ the proton.
What is a conjugate acid/base pair for H2O and OH-?
Here OH- is the conjugate base and H2O the acid.
What defines water-soluble bases?
Water-soluble bases are called alkalis and can produce OH- ions in aqueous solution.
How is a proton represented in aqueous solution for simplicity?
A proton in aqueous solution is represented by H+(aq) rather than H3O+(aq).
What is the relationship between hydrogen and protons?
An H+ ion is just a proton, formed when a hydrogen atom loses its electron.
What size comparison is made regarding protons and other chemical entities?
A proton is about 1 x 10^-15 m in diameter, compared with 1 x 10^-10 m or more for any other chemical entity.
What unusual properties does a proton have due to its size?
The extremely small size and intense electric field of a proton cause it to have unusual properties compared with other positive ions.
True or False: A proton is often found isolated in aqueous solutions.
False. A proton is never found isolated; it is always bonded to at least one water molecule.
Fill in the blank: Bases are substances which react with acids to _______.
[neutralise]
What is the definition of an acid according to Bronsted theory?
A substance that donates a proton (H ion)
What is the definition of a base according to Bronsted theory?
A substance that accepts a proton
What is the conjugate acid of HCl?
H3O+ (hydronium ion)
What is the conjugate base of NH4+?
NH3 (ammonia)
True or False: The product of [H⁺] and [OH⁻] in water is constant.
True
Fill in the blank: The ionic product of water (Kw) at 298 K is equal to _______.
1 x 10^-14 mol²/dm⁶
What happens to the concentrations of H⁺ and OH⁻ when one increases?
The other must decrease proportionately
What does the ionization of water produce?
H⁺ (aq) and OH⁻ (aq)
What is the equilibrium expression for the ionization of water?
Kw = [H⁺][OH⁻]
In pure water at 298 K, what is the concentration of H⁺?
1 x 10^-7 mol/dm³
What is the size of an H ion compared to other chemical entities?
About 1 x 10^-15 m in diameter
Why is an H ion never found isolated in aqueous solutions?
It is always bonded to at least one water molecule
What is the representation used for a proton in an aqueous solution?
H⁺ (aq)
What does the term conjugate acid-base pair refer to?
An acid and its corresponding base that differ by a proton
How do you calculate pH ?
1)First, write down the H+ concentration of the solution.
2) State natural log of H+ equal..
3) Calculate log 10.
4) Then calculate negative log 10 of the previous answer.
5) Write the final answer.
True or False
Using this pH definition,
a difference in one pH means that the acidity is ten times greater
For instance, pH 3 is ten times as acidic as pH 4
True
What are diprotoc acids ?
These are acids in which one molecule dissociates to give two protons.
What were Diprotic acids used to be called?
Dibasic acids
There are no H+ ions in an alkaline solution .
True or False ???
False
What is acid rain ?
Acid rain is the release of sulphur dioxide into the air through the smoke from factories. Sulphuric dioxide is bonded to water molecules and becomes a part of the water 💧 cycle.
Explain the entire process of acid rain.
Sulfuric acid is a factor of acid rain. Sulfur dioxide (SO2) within the atmosphere bonds with water and oxygen to form acid. The sulfuric acid disintegrates into he cloud water (water vapour) and water droplets, then falls as acid rain.
How did cattle survive acid rain 19th and 20th century ?
Some cattle are thought to have survived the smogs because ammonia from their urine neutralised the acid gases.
What was the estimated pH of acid rain during the 19th and 20th century?
Less than 2
Who wrote the play Brand ?
Norwegian playwright Ibsen
Who are the people who still complain about acid pollution today from Britain ?
The Scandinavians
What is flue gas desulphurisation ?
This process involves passing gaseous combustion products through a suspension of calcium hydroxide and reacts with sulphuric acid to produce calcium sulphate or gypsum.
Does calcium hydroxide react with any acidic gases to produce salts ?
Yes
Burning of petrol in car engines can cause ______________________.
Some nitrogen is released into the atmosphere and combines with oxygen to form the nitric oxide (NO) and nitrogen dioxide (NO2)
What are two effects of Acid Rain ?
The death of fishes 🐟 🐠
The death of trees 🌳 🌴
Acid rain kills fishes by causing ______________________ and ______________________.
an increase in acidity of lakes and streams
leaching poisonous aluminium ions out of the soil and into water bodies.
Trees are killed by Acid Rain. This occurs when _____________and_______
_______.
trees absorb acid through their roots and their leaves.
