acid and bases Flashcards by Unknown Unknown

when we mix acids with water, whats released?

hydrogen ions (H+) are released

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in water H+ forms what which makes a solution acidic?

they form hydroxonium ions (H3O+). its these ions that make a solution acidic

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when bases are mixed with water, they react with….. to form …….

when we mix bases with water they react with H+ ions to form hydroxide ions (OH-)

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WHATS A bronsted lowry acid

a proton donor

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whats a bronsted lowry base

proton acceptor

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when acids and bases react with water they form what type of reaction. give examples of weak and strong acids and bases, their equations and whether the forward or backward reaction is favoured for each.

reversible reaction
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strong bases and strong acids dissociate ……… in water

dissosciate completely

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weak acid and weak bases dissosciate ……. in water

partially

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when acids and bases react together, protons are …. give generic examples of this occuring

exchanged.
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where does equilibrium lie in strong acids and in weak acids

strong acids: eqm lies well over to the righjt
weak acids: eqm lies well over to the left

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why does the kw expression not involve water (ionic product of water)

water dissociates into its ions very weakly hence water has a constant value

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the value of kw is the _____ in a solution at a given temp

the same

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kw at a given temp has a value of…

1 * 10^-14 mol^2 dm^6

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kw changes if what

temp changes

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when is the conc of h+ and oh- the same

[H+] = [OH-] in pure water

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when referring to pure water, kw can newly become

[h+]^2

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define ph

a logirithmic scale that measures the conc of h+ ions in solution

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kw expression

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for strong acids, what can we assume in terms of conc of h+ and conc of acid

we can assume [H+] = [acid] for strong acids, whereas we cant with weak acids

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give the Ka expression for weak acids, and teh eqm constant weak acids exist in.

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when is the conc of H+ = to the conc of A-, and hence what would the ka expression simplify to in this scenario.

when the dissosciation of acid is greater than the dissosciation of water present in the solution, hence we can assume all H+ ions come from the acid. [H+] = [A-].
Ka = [H+]^2 / [HA]

whats pKa

another way of measuring the strength of an acid similar to pH.

the lower the value fo pKa, the what?

the stronger the acid.

pka formula

pka=-log10 ka

titrations can be used to work out the ...

conc of an acid or base

graphs showing ph against volume of base added from a titration. they show diff combos of weak and strong acids and bases.

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in a titration curve, what does the equivalence point/end point indicate? and show it

its at this point that acid has been neutralised fully by the base. https://merchanttaylorsschools-my.sharepoint.com/:w:/g/personal/tofoma_merchanttaylors_com/Ef2tksibwSRDnIIIHkl60eoBL3dV4U4_frm1jkAMGOJtFg?e=8Nzm2l

S shaped graph is when whats in the conical flask, and reverse S shape is when what

S shaped, means the acid is in the conical flask and the base is in the burette, reverse S shape means base is in the conical flask and acid is being added in the burette,

whats the half neutralisation point and whats its use, and show how we can use it

this is the point half way between 0 and the equivalence point. it can be used to calc the pKa of a weak acid by taking the PH at this point. (using a ph meter) https://merchanttaylorsschools-my.sharepoint.com/:w:/g/personal/tofoma_merchanttaylors_com/Eb1qnGIOKxVAjf00VPVaLzgBq8qFy3ql6S1hkSRo4KG8YQ?e=EeYNzc

equivalence point vs half neutralisation point in terms of H+ ions

in the equivalence point no H+ ions are left they have all reacted, whereas in the half neutralisation point , the amount of H+ ions are the same as the amount of oh- ions added (they are equal in amount)

why is an indicator used in a titration?

to determine the endpoint

for an indicator to be effected at determining the end point, what must happen

it must change colour ENTIRELY within the vertical part of the titration curve

for a titration ), whats the PH range the indicator must change colour and give the options of indicators as well as give the types of titration where u can use each indicator

range: 3 and 10. indicators which caN BE USED: methyl orange, and phenolphthalein. methyl orange - colour change - ph 3-4.5 phenolphtalein colour change - ph 8.2 - 10. METHYL ORANGE IS RED AT LOW PH AND YELLOW AT HIGH PH VALUES. IT CAN BE USED FOR THE FOLLOWING: STRONG ACID/ STRONG BASE STRONG ACID/ WEAK BASE PHENOLPHTHALEIN IS COLOURLESS AT LOW PH AND PINK AT HIGH PH VALUES IT CAN BE USED IN WEAK ACID/STRONG BASE https://merchanttaylorsschools-my.sharepoint.com/:w:/g/personal/tofoma_merchanttaylors_com/EWxHfjRaDsdFptiBeEtol3kBSVx9GC71lCZ3NBbdPCCn5Q?e=cxxt7R

WEAK ACID/WEAK BASE TITRATIONS HAVE NO SHARP PH CHANGE, HENCE NO INDICATOR IS SUITABLE SO WHAT DO U USE

A PH METER

diprotic acids release what

2 protons when they dissociate in solution

when a diprotic acid reacts with a base, why is it neutralised in 2 steps

because 2 protons are released from the acid molecule separately i.e they dont both leave at the same time.

diprotic acidv base titration curve

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WHAT IS A BUFFER

A BUFFER IS A CHEMICAL THAT RESISTS THE CHANGE IN PH WHEN SMALL AMOUNTS OF ACID OR BASE ARE ADDED. (BUFFERS DO NOT STOP THE CHANGE IN PH JUST RESIST IT)

2 TYPES OF BUFFER\

ACIDIC OR BASIC BUFFER

WHATS AN ACIDIC BUFFER

ACIDIC BUFFER IS A BUFFER WHICH RESISTS THE CHANGE IN PH IN ORDER TO KEEP THE SOLUTION BELOW PH7. THEY ARE MADE FROM A WEAK ACID AND ITS SALT

AN EXAMPLE OF AN ACIDIC BUFFER IS USING ETHANOIC ACID CH3COOH (WEAK ACID) AND SODIUM ETHANOATE CH3COO-NA+ (ITS SALT). IN ANY BUFFER SOLUTION THERE ARE 2 EQUILIBRIUM EQUATIONS AT PLAY. THE 2 EQUATIONS CO-EXIST IN THE SAME BEAKER. GIVE THE EQUATIONS, AND SHOW WHERE THE EQM LIES stating how well the weak acid/salt dissosciates, as well statign what happens we we add an acid (H+) to the buffer, as well as when we add a base (OH-) to the buffer?

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what is a basic buffer

a buffer the resists changes in ph in order to keep the solution above ph7. they are made from a weak base and its salt.

AN EXAMPLE OF AN basic BUFFER IS USING Nh3 ammonia (WEAK base) AND ammonium chloride (ITS SALT). IN ANY BUFFER SOLUTION THERE ARE 2 EQUILIBRIUM EQUATIONS AT PLAY. THE 2 EQUATIONS CO-EXIST IN THE SAME BEAKER. GIVE THE EQUATIONS, AND SHOW WHERE THE EQM LIES stating how well the weak base/salt dissosciates, as well stating what happens we we add an acid (H+) to this basic buffer, as well as when we add a base (OH-) to the basic buffer?

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to calculate the ph of a buffer, you need to know what? in order to find what

the Ka value and the concentration of the weak acid/base and its salt. in order to find [H+0 and hence the ph can be found from there

what does it mean to calculate the ph change of a buffer

this is when you add a small amount of acid or base to buffer and calculate the change in PH.

example question on calculating the ph change of a buffer

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Uses of buffers

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