Acids and Redox

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Define an acid.
A species that is a proton (H+ ion) donor
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What happens when an acid is added to water?
The acid splits into its component ions and releases H+ ions
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What are the three common acids used in AS chemistry and what is their formula?
1) Sulfuric acid (H2S04) 2) Hydrochloric acid (HCl) 3) Nitric Acid (HNO3)
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Formic acid found in insect bites/stings is known by what other name?
Methanoic acid
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Define a base.
A species that is a proton (H+ ion) acceptor.
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What are the two types of common bases? Give examples of each.
1)Metal oxides- e.g. MgO K2O 2)Metal Hydroxides e.g. NaOH, Mg(OH)2
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What is another group of common bases?
The amines e.g. ammonia (NH3) and (methylamine CH3NH2)
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What is an alkali?
A type of base that dissolves in water to give aqueous hydroxide (OH-) ions
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What are the common alkalis used in AS chemistry and what are their formulas?
Sodium Hydroxide (NaOH) , Potassium Hydroxide (KOH) and Ammonia (NH3)
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What are two uses of bases in everyday life?
1) MgO is in milk of magnesia to combat acid indigestion. Calcium Hydroxide Ca(OH)2 is used to neutralise acidic soils
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What is the main problem caused by cheap indigestion tablets.
They use metal carbonates as a base as the carobnate is often a cheap filler ingredient. This effectively neutralises the base but produces carbon dioxide in the process which can leave people feeling very bloated.
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Give two examples of alkalis used in everyday life.
Bleach and soap( which is made by reacting an alkali with fat)
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what happens in a neutralisation reaction?
The H+ ions from the acid react with the OH- ions from the alkali and water is formed
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Ph of acids and bases.
acids= less than 7.0 bases= greater than 7.0
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What happens when a weak acids dissolves in water?
The acid only releases a small proportion of its available hyrogen atoms into the solution as H+ ions. It PARTIALLY DISSOCIATES in aqueous solution.
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What does an equilibrium sign indicate for the reaction of an acid with water
that the forward reaction is incomplete
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Acid+ Base=
Salt+Water
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What can a titration be used to find?
1) the concentration of a solution 2) the identity of unknown chemicals 3) the purity of a substance 4) the molar mass 5) the number of moles of crytallisation
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what do we use to prepare a standard solution?
a volumetric flask
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Where do we measure from?
The bottom of the meniscus
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Where should the meniscus be viewed at?
Eye level- for accuracy.
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How do we know when the end point has been reached?
When there is a distinct colour change in the solution in the volumetric flask.
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What is the end point colour of the following indicators?
Methyl orange= orange, Bromothymol blue= green, phenolphthalein (base to acid= pale pink) ( acid to base=colourless)
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What is each burette reading measured to? What does this mean?
the nearest 0.05 cm. Each burette reading will have a reading to the nearest 2 decimal places and the last digit will either be a 0 or a 5
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What error could occur if you didn't invert the volumetric flask several times
the solution used in the first titration would be more dilute than the solution used later meaning the first titre would require less solution.
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What are concordant results?
results that agree within 0.10cm3
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Define oxidation number.
The number assigned to and atom or ion to describe its relative state of oxidation or reduction
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Oxidation Rule: In covalent compounds...
one element must have a positive ON and another element must have a negative, so overall they equal zero
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Oxidation Rule: Hydrogen is +1...
except in metal hydrides where it is -1
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Oxidation Rule: Chlorine is -1 ...
except in compounds with O and F
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Oxidation Rule: Oxygen is -2...
except in peroxides where it is -1
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Define oxidation and reduction.
Oxidation= loss of electrons+ increase in ON, Reduction= gain of electrons+ decrease in oxidation number.
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What is an oxidising agent?
A substance that causes another substance to be oxidised in a reaction. It is a good receiver of electrons and thus is reduced in the reaction.
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Oxidation Rule: Fluorine is...
ALWAYS -1
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What is a reducing agent?
A substance that causes another substance to be reduced in a reaction. It is a good donator of electrons so it is oxidised in the reaction
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Why are roman numerals used in the naming of some compounds/ions?
As some elements form ions with different charges the roman numeral shows the relative charge of the ion and thus its oxidation state
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Acetic acid present in vinegar is also known as?
Ethanoic acid
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Oxidation Rule: The sum of all the Oxidation Numbers in a polyatomic ion...
equals the overall charge on the ion.
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What would be the effect of an air bubble in the pipette during a titration
The titre would be less than it should be because less solution would be added to the pipette volume.
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What is unusual about sulfuric acid?
It first behaves as a strong acid as one of its H atoms is released. However the resulting HSO4- ions then only partially dissociate so it then behaves as a weak acid. (Other atoms containing more than one H atom behave similarly.
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Other cards in this set

Card 2

Front

What happens when an acid is added to water?

Back

The acid splits into its component ions and releases H+ ions

Card 3

Front

What are the three common acids used in AS chemistry and what is their formula?

Back

Preview of the front of card 3

Card 4

Front

Formic acid found in insect bites/stings is known by what other name?

Back

Preview of the front of card 4

Card 5

Front

Define a base.

Back

Preview of the front of card 5
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