C4 Strong Acids and Weak Acids (pg 130) Flashcards
What do Acids produce in water?
Protons.
The thing about acids is they ionise in equeous solution - they produce hydrogen ions H+
These acids dont produce hydrogen ions until they meet water, so for example, hydrogen chloride gas isn’t acidic
HCl »_space;> H+ + Cl-
HN03 »_space;» H+ + N03-
Do STRONG ACIDS, eg; sulfuric, hydrochloric and nitric acids ionise completely in water?
Yes
All acid particles dissociate to release H+ Ions
Do WEAK acids (eg, ethanoic, citric and carbonic acids), ionise completely in solution?
No they do not fully ionise in solution. Only a small proportion of acid particles dissociate to release H+ ions
Is the Ionisation of a weak acid reversible reaction, and why?
yes the ionisation of a weak acid is a reversible reaction, which sets up an equillibrium between the undissociated and dissociated acid.
Since only a few of the acid particles release H+ ions, the position of equillibrium lies well to the left.
is this a strong or weak acid?
HCl »_space;» H+ = Cl-
Strong acid
Is this a Strong or Weak acid?
CH³COOH »_space;»»»> H+ + CH³COO-
««««<
Weak Acid
Reactions of Acids involve the H+ ions reacting with what?
other substances.
If the concentration of H+ ions is higher, what do this mean?
the rate of reaction will be faster, so strong acids will be more reactive than weak acids of the same concentration.
The pH of an acid or alkali is a measure of the concentration of what?
H+ ions in the solution.
pH is a measure of the concentration of Hydrogen Ions
What do pH stand for?
potential Hydrogen
what do equilibrium mean in chemistry?
the concentrations of reactants and products do not change. but the forward and reverse reactions have not stopped - they are still going on, and at the same rate as each other
what do ‘undissociated’ mean in chemistry?
not separated into ions, radicals or simpler atoms or molecules
What do ‘dissociation’ in chemistry mean?
the breaking up of a compound into simpler constituents that are usually capable of recombining under other conditions
For every decrease of 1 on the pH scale, the concentration of H+ ions increases or decreases by a factor of 10? explain your answer
H+ ions increases by a factor of 10.
So an acid that has a pH of 4 has 10 times the concentration of H+ ions of an acid that has a pH of 5.
For a decrease of 2 on the pH scale, what would the concentration of H+ ions increase by a factor of what? explain your answer?
H+ ions increases by a factor of 100.
The general rule for this is:
Factor H+ ion concentration changes by = 10-x
X is the difference in pH. so if pH falls from 7 to 4 the difference is -3, and the factor the H+ ion concentration has increased by is 10-(-3) = 10³
Is a pH of a strong acid LESS or MORE than the pH of a weaker acid if they have the same concenration?
The pH of a STRONG acid is always LESS than the pH of a weaker acid
Acid STRENGTH (i.e. strong or weak) twlls you what?
it tells you what proportion of the acid molecules ionise in water.
What do the concentration of an acid measure?
it measures how much acid there is in a certain volume of water. (concentration is basically how watered down your acid is)
Don’t confuse strong acids with cencentrated acids
The larger the amount of acid there is in a certain volume of liquid, the MORE OR LESS concentrated the acid is?
The more concentrated the acid is
so you can have a dilute (not very concentrated) but strong acid, or a concentrated but weak acid
Will pH increase or decrease acid concentration regardless of whether it’s a strong or weak acid?
the pH will DECREASE with increasing acid concentration
(concentration describes the total number of dissolved acid molecules - not the number of molecules that are ionised to produce hdrogen ions at any given moment)
Acids are acidic because of what?
H+ ions
Strong acids are strong because?
they let go of all their H+ ions at the drop of water
Name a strong acid?
either:
sulfuric acid
nitric acid
hydrochronic acid
A student added strong acid to a weakly acidic solution of pH6. The pH of the new solution was found to be pH3. By how many times did the concentration of H+ increase?
Change in pH = 3-6 = -3
Change in concentration of H+ = 10 ÷ -³ = 10³ = 1000
so the concentration of H+ is 1000 times greater at pH = 6
What is Sulphuric Acid?
it is a strong acid made by oxidizing solutions of sulphur dioxide and used in large quantities as an industrial and lab reagent.
The concentrated for is an oily, dense, corrosive liquid.
It is used in various concentrations, in the manufacture of fertilizers, pigments, dyes, grugs, explosives, detergents and inorganic salts and acids, as well as in petroleum refining and metallurgical processes.
Sulfurtic acid can irritate and burn the skin and eyes, and may lead to blindess. exposures may cause a build up of fluid in the lungs (pulmonary edema), a medical emergency. it can also cause headach, nausea and vomiting.
it is produced from sulfer, oxygen and walter (sulfer is burned to produce sulfur dioxide, this is then oxidised to sulfur trioxide using oxygen in the presence of a vanadium(V) oside catalyst)
What is Nitric Acid?
a colourless liquid, or pale yellow (older samples tend to be yellow due to decomposition into oxides of nitrogen), corrosive poisoness liquid acid with strong oxidizing properties, made in the laboratory by distilling nitrates with surphuric acid.
Nitric acid is used for the production of ammonium nitrate, a major component of fertilizers. It is also used for producing explosives like nitroglycerin and trinitroouene (TNT) and for oxidizing metals.
it is a strong acid with chemical formular HNO3.
Nitric acid is produced by oxidation of ammonia. the liquid ammonia is evaporated, superheated and sent with compressed air to a convertor, containing platinum and rhodium catalyst.
What is hydrochloric acid?
It is an aqueous solution of hydrogen chloride. It is a colourless solution with a distinctive pungent smell. It is a strong acid. It is a component of the gastric acid in the digestive systems of most animal species, including humans.
It is used for the netrualization of alkaline agents, and a bleaching agent, in food, textile, metal and rubber industries. It is neutralized if released into the soil, and it rapidly hydrolizes when exposed to water
It is made of Hydrogen Chloride (HCl), a compound of the elements gydrogen and chlorine. A gas at room temperature and pressure. A solution of the gas in water is called Hydrochloric acid
it is found in the gasses evolved from volcaneos, partucialry ones found in mexico and south america. and in the digestive tract of most mammals.
What is a catalyst in chemistry?
A catalyst is a substance that affects promotes or accelerates reaction of two or more substances to generate a different end product.
it is a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction.
example: Nickel (Ni) is used in hydrogenation of palm oil into margerine.
