Acids and bases

acids and bases are important in what contexts?

biological and an environmental context.

acids and bases are important in what type of chemicals?

industrial and agricultural

why are bases such as NaOH and Na2CO3 used in many cleaning products?

for their ability to react with oils and grease to produce water soluble soaps

what is the formula for carbonic acid

H2CO3

what is the formula for citric acid?

C6H8O7

what is a soluble base called?

an alkali

what are some properties of acids?

they turn litmus paper red, they tend to be corrosive, they taste sour, they react with bases, have a relatively low pH, and they conduct an electric current

what are some properties of bases?

they turn litmus paper blue, they are caustic and feel slippery, they taste bitter, react with acids, their solutions have a relatively high pH and the solutions conduct an electric current

what does corrosive mean?

Corrosive refers to substances that can cause significant damage to living tissue or materials by chemical reaction. Corrosive substances can degrade or destroy other substances upon

what does caustic mean?

Caustic refers to substances that can burn, corrode, or destroy organic tissue or severe chemical reactions due to their strong alkaline properties.

at first how were acids and bases defined?

they were defined by their observed properties, such as their taste, effect on indicators and reactions with other substances

what wea Antonio lavoisiers theory of acids and bases?

he thought that the acidic properties were due to the presence of oxygen. This theory applied to sulphuric acid, and nitric acid and phosphoric acid. it however did not apply to hydrochloric acid

what was Humphrey davy’s acid base theory?

he suggested that the acid properties of a substance was associated with hydrogen and not oxygen. He said that acids contain a replaceable hydrogen and also that acids react with bases to form salt and water.

How did Humphry Davy come to his conclusion on acids and bases?

from experimental observation that metals could displace hydrogen from acids .

what is an example that supports Humphry Davy’s theory?

When zinc is placed in hydrochloric acid, it displaces hydrogen, forming zinc chloride and releasing hydrogen gas.

what is a limitation of Humphry Davy’s theory?

It does not explain the behavior of all acids, particularly those without hydrogen, or the nature of acid-base interactions beyond displacement.

what is Arrhemnius’s acid base theory

acids are substances that dissociate (break apart) and ionise (form ions) in water, they also produce H+ ions. Bases dissociate in water to produce OH- ions. His theory also suggests that water is formed in acid base reactions

what does Arrhenius’s theory not consider?

it does not account for hydrolysis, does not account for acid base reactions that do not form water, cannot explain self ionisation in water, and it cannot explain the amphoteric nature of some substances.

What is hydrolysis?

Hydrolysis is the chemical breakdown of a compound due to reaction with water. This process involves the breaking of bonds in the compound, facilitated by water molecules, resulting in the formation of new substances. In hydration, the compound interacts with water

what is the Bronsted Lowry theory

an acid is a proton donor i.e donating a H+ ion to a base. And a substance that is a base will accept protons from an acid. This theory expands upon Arrhenius's by focusing on proton transfer rather than just aqueous dissociation. It also includes acid-base reactions occurring in non-aqueous solutions.

why is bronsted Lowry the best definition of acids and bases?

•Accounts for hydrolysis

•Explains amphoteric substances.

•Can explain self ionisation of water.

•In summary unlike Arrehnius and Davy’s theory Bronsted and Lowry defined acids in terms of behaviour and not their chemical composition.

what is a hydrolysis reaction?

this occurs when a molecule or ion in aqueous solution reacts with water, either accepting or donating a proton

why is the reaction between hydrogen chloride and ammonia significant in supporting the bronsted Lowry theory?

It demonstrates how hydrogen chloride donates a proton to ammonia, forming ammonium chloride, illustrating acid-base behavior based on proton transfer. The Hcl and ammonia reaction is ab aqueous solution will just from ions. But if the HCl and ammonia are solids- it will form ammonium chloride. In each case the acid donates a proton to a base.

what are some limitations to the bronsted Lowry theory

in the reaction between calcium oxide and carbon dioxide, they produce the salt calcium carbonate but the theory does not account for reactions that do not involve proton transfer

what is a conjugate acid- base pair?

are two species that differ by a proton ; the conjugate acid is formed when a base gains a proton, while the conjugate base is formed when an acid loses a proton.

do strong acids hydrolyse in water?

no, this is because their conjugates are weak and cannot readily accept or donate a proton.

string bases are…

oxides and hydroxides of G1 and G2 elements

strong acids are…

all inorganic acids accept , H2O, H3PO4, HF, H2CO3

what is an inorganic acid?

An inorganic acid is a type of acid that does not contain carbon-hydrogen (C-H) bonds and typically releases hydrogen ions (H+) when dissolved in water. Examples include hydrochloric acid, sulfuric acid, and nitric acid.

weak acids are…

organic , but also H2O, H3PO4, HF, H2CO3

concentrated and dilute measures what?

the amount of solute per unit volume go the solvent

strength and weakness is a measure of what?

how well an acid or bae dissociates or ionises in water to produce hydrogen ions (H+) or hydroxide ions (OH-).

what is an amphiprotic substance?

is a substance that is able to donate or accept protons, depending on what they are reacting with. Therfore they can behave as either acids or base.

what is an example of an amphiprotic substance?

when water reacts with HCl it acts as a base, but then it reacts with NH3 it acts as an acid. Therefore water can act as either an acid or base dependant on the solute present.

if the solute is stronger acid than water how will the water react?

as a base

if a solute is a stronger base than water how will the water react?

as an acid

what happens when an amphiprotic substance is placed in water?

it reacts as both an acid and a base. For example HCO3- (hydrogen carbonate) can donate a proton to form CO3^2- or accept a proton to form H2CO3. Although both of these reactions are possible, one will dominate and can be identified by the pH being measured

what is a monoprotic acid?

it is an acid that can only donate one proton per molecule

what are some examples of monoprotic acids?

HCl, CH3COOH, HNO3 and HF

why is only one of the hydrogen atoms from acidic acids able to be donated

only the hydrogen that is part of the highly polar O-H bond is donated. this hydrogen atom being called the acidic proton.

what is a polyprotic acid?

an acid that is able to donate more than one proton per molecule. The number of hydrogen ions an acid can donate depends on the structure of the acid. Polyphonic acids do not donate all of their protons all at once, the do so in steps when reacting with a base

what are diprotic acids

Acids that can donate two protons per molecule during reactions. Examples include sulfuric acid (H2SO4) and carbonic acid (H2CO3).

why is sulphuric acid described as a strong acid in water?

this is because it readily donates a proton and so this stage occurs almost to completion. virtually no H2SO4 molecules are found in an aqueous solution . This indicating that the H2SO4 fully ionises to produce HSO4- ions which can then react further to produce SO4 2- ions.

why is HSO4 - described as a weak acid?

because it only partially ionises in solution to form hydrogen ions and SO4 -2 ions and does not completely donate its proton, meaning some HSO4- remains undissociated. Therefore its ionisation reaction has a double arrow, indicating an incomplete reaction occurs and an equilibrium is established. Therfore this indicates that a solution of sulphuric acid contains hydrogen ions and hydrogen sulphate ions and sulphate ions

what is a triprotic acid?

are acids that are able to donate 3 protons per molecule, an example is phosphoric acid, H3PO4 which fully dissociates in a stepwise manner to release three hydrogen ions.

what is the strength of phosphoric acid, and how does that effect it being a triprotic acid?

it is a weak acid, this means with each step of ionisation, it only partially dissociates before reaching an equilibrium, resulting in an incomplete donation of its protons. Thus, while it can donate three protons, the strength of each ionisation decreases as more protons are released.

how does Bronsted Lowry define the strength of acid or a base?

the strength of an acid as its abilirty to donate hydrogen ions to a base. And the strength of a bee is defined as the measure of its ability to accept hydrogen ions from an acid .

name 3 strong acids?

HCl, H2SO4, HNO3. therfore when these molecule ionise in water there is virtually no unreacted acid molecules remaining

name 3 weak acids?

H2CO3, CH3COOH, H3PO4

name 3 strong bases

NaOH, Ca(OH)2, KOH

name a weak base?

NH3

what elements are bonded by a covalent molecular bond

non metal and non metal

what bonding is present ethanoic acid?

polar covalent molecular

what is an ionic compund made up of?

a metal and a non metal

the stronger the acid the….. its conjugate base

weaker

why is ethanoic acid classified as a weak acid?

because the equilibrium constant for the hydrolysis reaction is small. This means that it does not fully dissociate in water, resulting in a comparatively low concentration of hydrogen ions.

what is the equilibrium constant for a hydrolysis reaction?

Ka= [Products]/ [reactants]

why does water not appear in the equilibrium constant?

because water is the solvent and its concentration is virtually constant in an aqueous solution.

what is the symbol for the basicity constant in a hydrolysis reaction?

Kb

strength versus concentration?

if you bubbled a large amount of HCl into water in one beaker but only a small amount in another beaker with the same amount of water they would have different concentrations. however they both would completely ionise in a solution and therfore both are strong

pure water undergoes self ionisation in a …

very small extent producing both OH- ions and H3O+ ions- therfore acting as an amphiratoric substance

what is the ionisation constant of water at 25 degrees?

Kw= [H3O+][OH-]= 1.00X10^-14, meaning in an aqueous solution if OH- ions increases, then H3O+ must decrease proportionally

considering the ionic constant, for a solution to be acidic the concentration of H3O+ ions must be what?

higher than 1.00 ×10^-7 molL-1 at 25 degrees

what is the formula for determining the pH of a a solution?

pH= -log[ H3O+]

what is the formula for determining the concentration of H3O+ ions from pH?

[H3O+]= 10^-pH

the pH of a solution… and the amount of H3O+ ions ….

decreases, increases

what should the pH of the blood be?

7.35-7.45 and length of deviation can cause serious illness or death

what happens to the value of Kw as the temperature increases?

Kw will also increase, this is because the set ionisation of water is an endothermic reaction

how do you calculate the new concentration of a diluted solution?

C2=C1V1/V2, where the V2 is initial volume plus the volume added

if an acid is repeatedly diluted what would happen to the pH?

the pH will keep increasing, howver will not go above 7

if a base is repeatedly diluted what would happen to its pH?

its pH will keeps decreasing, however it will not go below 7

what is a salt?

is an ionic compund that that contains a positive cation other than a hydrogen ion and a negative ion (anion) other than oxide ion O2-, or OH- ion

what are the three types of hydrolysis?

acidic (H3O+ formed) basic (OH- formed) and neutral (neither ions formed)

how can a salt be either acidic or basic?

the salt can dissociate in water to form ions, those ions can have further acid/ base reactions with water- forcing water to either act as an acid or base forming OH- or H3O+ ions

in a salt where does the anion and cation come fro?

anion from acid, and cation from base

transition metals with charges 2+ and 3+ and metals from group 13, do they undergo acidic or basic hydrolysis?

acidic

what group from the periodic table does not undergo hydrolysis?

group 1

if the salt has come from a strong acid and strong base, what will the PH be?

it will be neutral because both conjugates will be weak and will not undergo hydrolysis

if a salt comes from a strong acid and a weak base what will the PH be?

it will be an acidic salt, because the conjugate from the weak base would be a strong acid that will undergo hydrolysis and form/ release H3O ions, decreasing the pH levels

if a salt comes from weak acid and a strong base what is its PH?

the salt will be basic, this is becasuse the conjugate of the weak acid is a strong conjugate base that will hydrolyse in water forming OH- ions (acting as a bronsted and Lowry base) and therfore increasing pH making the salt basic

if a salt comes fro a weak acid and a weak base what is the final PH?

can only be measured from a PH meter to determine the exact pH, as it depends on the strengths of the conjugate acids and bases involved as they both will undergo hydrolysis. the PH will depend upon the extent to which each of these completing reaction occurs. To find the PH you would need to examine their equilibrium constants to evaluate their contributions to the pH. (either the acid or base with the highest K value will influence the PH)

how is the PH influenced by polyprotic acids during hydrolysis?

The pH is influenced by polyprotic acids as they can donate multiple protons, leading to a series of hydrolysis reactions. Each dissociation step contributes to the overall acidity, resulting in varying pH levels depending on the strength and concentration of the individual dissociated species.