Chemistry topic3 Flashcards
What is red litmus paper used to test for?
Alkalis
What colour does red litmus paper turn if alkali is added
Blue
What is blue litmus paper used to test for?
Acids
What colour does blue litmus paper turn when an acid is added..?!
Red
What ion causes acidity?
The hydrogen ion - H+
the pH scale is a measure of the ? of hydrogen ? in a solution and hence its ?
concentration,ions, acidity
what does pH stand for
p stands for Potenz (meaning power in German) and H stands for H+
what type of a scale is the pH scale?
a logarithmic scale
what does pH being a logarithmic scale mean
it means a solution of pH 1 has 10 times as many hydrogen ions than a solution with a pH of 2
What are the two main ways of finding the pH of a solution?
By using a universal indicator
By using a pH meter
There are 6 main acids, what are they
Hydrochloric acid, nitric acid, sulphuric acid, phosphoric acid, ethanoic acid and carbonic acid
Give the chemical formula of phosphoric acid
H3PO4
Give the chemical formula of ethanoic acid
CH3COOH
Give the chemical formula for carbonic acid
H2CO3
What happens when a metal and an acid combine?
A salt is formed
give the balanced chemical equation for the reaction between magnesium and hydrochloric acid
Mg + 2HCl —> MgCl2 + H2
What are the products of a reaction between a metal and an acid
A halide is formed with the hydrogen in the acid replaced with the metal, leaving left over hydrogen eg: MgCl2 + H2
? of acids are made by dissolving certain covalent ? in ? the water causes the ? molecules to break ? in a way that generates ? ions
solutions, molecules, water, covalent, apart, hydrogen
What does concentrated and dilute refer to in acids
The amount of acid molecules dissolved in water!! x
Will a concentrated acid have a large or little amount of acid molecules dissolved in a certain volume of water?
Large because it is concentrated meaning lots of particles all in the same volume in comparison to dilute where there’s a lot less particles
What are the two words for acid molecules getting split apart
1.Dissociation
2.Ionisation
What does strong and weak refer to in acids
How many of the acid molecules have been split apart into ions
What three acids are the main strong acids?
HCl, H2SO4 and HNO3! x
What will happen to a strong acid when dissolved in water
It will compeltely dissociate into ions - so all the acid molecules will split apart and form hydrogen ions
What happens when a weak acid dissolved in water
only a small proportion of the molecules dissociate into ions - so lots of undissociated moleculesss and a low number of ions
Which acid is a weak acid?
Ethanoic acid
What does the reversible arrow mean?
It shows that a reaction cannot go to completion because not all molecules are dissociated
Example of ethanoic acid and the reversible arrow
CH3COOH reversible arrow CH3COO- + H+, this shows how it is incomplete because not all of the ions have been dissociated so the arrow shows this
bases are ? that can ? acids
substances, neutralize
bases are normally metal ? or metal ?
oxides, hydroxides
alkalis are ? which are soluble in ? - so they are a ? group of bases
bases, water, sub
Alkalis are generally what?
Hydroxides
All alkalis will either ? in water or react with ? to produce ? ions
dissolve, water, hydroxide
Strong alkalis will compeltely ? in water to give a ? conc of ? ions
dissolve, high, OH-
Weak alkalis will only ? react with water to give a ? conc of ? ions
partially, low, OH-
What are 2 examples of strong alkalis
Sodium hydroxide and potassium hydroxide
What is an example of a weak alkali?? x
Ammonia
What other substance can bases be?
Metal carbonates
what colour is litmus solution in acid, water and alkaline?
orange, light purple, and same purple
how do you know a solution is not acid, neutral but an alkali
by using phenolphthalein- which makes alkalis turn pink, but acids and neutral solutions stay colourless
what colour is universal indicator in acid, water, and alkaline
red, green and dark purple
what colour is methyl orange in acid, water and alkaline?
neon pink, orange, and yellow
difference in reactivity between strong and weak acids…
strong acids react ? and more exothermically than ? acids of the same ?, as they contain more ? ions as strong ? are completely ?
faster, weak, concentration, H+, acids, dissociated
what are the products of a reactive metal + acid
metal salt and hydrogen
what are the products of a base(alkali) and an acid?
metal salt + water
what are the products of a metal carbonate and acid
metal salt + water + carbon dioxide
what is the product of ammonia and acids?
ammonium salts
what’s the ionic equation for an acid and a hydroxide?
H+ + OH- —> H20
what’s the ionic equation for acid + oxide?
O2- + 2H+ —> H20
ionic equation for acid + carbonate?
2H+ + C03(2-) —> H20 + CO2
ionic equation for ammonia + acid?
NH3 + H+ —> NH4+
what’s the ionic equation for acid + hydrogen carbonate?
H+ + HCO3- —> C02 + H20
solubility rules: which substances are always or almost always soluble and what are the exceptions?
all potassium, sodium and ammonium salts are soluble, as well as all nitrates, and all halides - apart from lead and silver ones, and all sulphates apart from calcium, barium and lead
Which substances are insoluble - solubility rules and what are the exceptions?
All carbonated and hydroxides aside from potassium, sodium and ammonium substances
what is a precipitate reaction?
a reaction between two soluble solutions, which give a product of a soluble solution and an insoluble solution - the precipitate
silver nitrate experiment - why does the colour change from white to silver when exposed to the light?
the UV light makes it change colour to silver
what was silver nitrate originally used in?
old photographs - lying them in the light would allow them to develop
precipitation method - how to make an insoluble ? -
choose ? suitable solutions. one ? must contain the positive ion - the ? . the other must contain the ? ion - the ? - both solutions must be ? and it is easiest to choose a ? nitrate (as all nitrates are ? ) and a sodium compound that contains the ? ion (as all ? compounds are soluble )
salt, two,solution, cation, negative, anion, soluble, metal, soluble, negative, sodium
in titration experiment what do you measure the hydrochloric acid with?
the Burette - a sort of topless measuring cylinder with a tap
in titration what measures the sodium hydroxide
the glass pipette
why is titration needed - instead of the excess base method?
the excess base method relies on the salt and base being easily separated by filtration, but in reactions with soluble salts or compounds a different method needs to be used - in this case titration
what do you need to do and what happens in the copper sulphate reaction?
mix excess copper oxide with sulphuric acid, then filter the excess copper oxide off - leaving the filtrate - copper sulphate. then gently heat the copper sulphate till saturated and then leave it to cool for a couple of days in a warm place so it can crystallize but not all the water evaporate
what happens in the sodium chloride and silver nitrate reaction?
mix together silver nitrate and sodium chloride - should turn milky white bc of the precipitate forming. then filter it and add some water to wash off any extra sodium nitrate or unreacted reactants (also discard the filtrate). then once this is finished lay out the paper on a mat and place a smaller opaque tile across the filter paper so it covers half the solid. then wait and expose to light and half of it should go silver and half should stay white
what does saturated solution actually mean?
it means it has the maximum capacity of dissolved solute in the solvent x
what happens in the reaction between metal carbonates (or hydrogencarbonates) and acids?
fizzing, and the carbonate ‘dissolves’
what happens in the reaction between metal oxides or hydroxides and acids
- if a solid base is added it will dissolve
- if an alkali is added, the reaction will be exothermic
what happens in a reaction between a (reactive) metal and acid?
-fizzing
-the reactive metal dissolves
-exothermic reaction
what does exothermic mean?
gives out energy, very hot
what is the reaction to make an insoluble salt called
precipitate reaction
what is the reaction to make a soluble salt that isn’t ammonium sodium or potassium
excess base method
what is the reaction to make a soluble -ammonium, sodium and potassium salt called
titration!!
excess ? method :
react the appropriate acid with an ? of solid and ? base ie oxide, hydroxide or ? , if in doubt use metal ? and acid
base, excess, insoluble, carbonate, oxide
titration method -
react the ? acid with the appropriate ? (or carbonate) use NaOH/KOH or ?
appropriate, hydroxide, NH3
if in doubt in a precipitation method what two substances would you use?
metal nitrate and sodium salt
monitoring the pH of a reaction experiment - what are the reactants?
calcium hydroxide and Ethanoic acid (vinegar)
what does calcium hydroxide and Ethanoic acid react with each other to make?
calcium ethanoate and water
what happens in the neutralisation reaction between the calcium hydroxide and the Ethanoic acid?
as you add more and more CaOH the pH of the acid increases - slowly at first - 2,2.3,2.6 etc but then at 5 it has a massive jump to about 12 - going from a weak acid to an alkali
in the neutralisation reaction between the calcium hydroxide and the Ethanoic acid does it smell of vinegar at the end?
no because it has been neutralized
what are the two best apparatuses at measuring the volume of a liquid (apart from a measuring cylinder)
burette and a glass pipette
what is the general word equation for an alkali metal reacting with water
metal + water -» metal hydroxide + hydrogen
