Metals, Alkalis And Salts Flashcards
The acidity or alkalinity of something is measured in…
pH
… Can be used to measure the approximate pH of a solution
Universal indicator
pH indicators are…
Chemicals that change colours at different pHs
Common pH indicators are…
Universal Indicator
Litmus Paper (red in acid, blue in alkali
Methyl orange
Phenolphthalein
Phenolphthalein is which colours?
Colourless in acidic or neutral
Pale pink in pH 9
Pink in alkali pH 10 - 14
Methyl Orange is which colours?
Red in acid pH 0 - 3
Orange at pH 4
Yellow in neutral and alkali pH 5 - 14
Litmus paper is which colours?
Red in acid pH 0 - 5
Purple at pH 7
Blue in alkali pH 8 - 14
Alkalis are sources of…
OH- ions
Acids are sources of…
H+ ions
Metal and Acid reactions are both … And …
Redox and neutralisation
Hydrochloric acid reacts with metals and metal compounds to form
A metal chloride
Sulphuric acid reacts with metals and metal compounds to form a…
Metal sulphate
Metal + Acid =
Salt + hydrogen
MASH is a … Reaction
Redox
What are the half equations for this?:
Mg + 2HCl = MgCl2 + H2
Mg = Mg(2+) + 2e-
2H(+) + 2e- = H2
Metal Oxide + Acid =
Salt and water
Metal oxide + acid is a … Reaction
Neutralisation
Metal Carbonate + Acid =
Salt + Water + Carbon Dioxide
Metal carbonate + acid is a … Reaction
Neutralisation
How to prepare soluble salts using titration (finding the exact amounts needed for neutralisation)
- A burette is filled with HCl
- A known quantity of alkali is in a conical flask
- The alkali contains an indicator
- the tap on the burette is opened to drop the acid in drop by drop
- when enough acid has been added to neutralise the alkali, the indicator will change colour and you turn off the tap
- the titration can be repeated using the same amounts without an indicator to contaminate any possible crystals
The process of making a solid come from a solution is called..,
Precipitation (the solid is called a precipitate)
An insoluble salt can be made by…
Reacting the appropriate soluble salt with an acid or an alkali or another salt
Prepare silver chloride
Use a soluble silver salt
Use a soluble chloride
(All nitrates and all sodium salts are soluble so they are safe bets I.e. Silver nitrate and sodium chloride)
What is the bromsted-Lowry theory?
An acid donates a proton
A base accepts a proton
Hydrochloric acid is a solution of…
Hydrogen chloride in water
When hydrogen loses its only electron it becomes a…
Hydrogen ion, which is just a proton
When hydrogen chloride dissolves in water…
A proton (the hydrogen ion) is transferred to the water.
The equation for hydrogen chloride dissolving in water is…
H2O(l) + HCl(g) = H3O+(aq) + Cl-(aq)
A H3O+ ion is called a…
Hydroxonium ion. We normally write it as H+(aq), and you can think of it as a hydrogen ion riding on a water molecule
Water is a … Molecule
Polar
Polar molecules are…
Slightly negative at one end (e.g. The oxygen in water) and slightly positive at the other (e.g. The hydrogen in water)
When something such as sodium chloride is being dissolved in water…
The slightly positive ends of the water molecule cluster around the negative chloride ions, while the positive ends cluster around the sodium. The water molecules then literally pull apart the sodium chloride crystal
To break bonds (between the salt + and - ions and between the water molecules) you need …, therefore … Reactions are unlikely
Energy, therefore endothermic processes are unlikely. If a substance is soluble it is because more energy is formed when water molecules make strong bonds to the salt ions, paying back the energy required to break bonds
Polar molecules ‘pulling’ works on…
Not every substance. E.g. MgO is only slightly soluble due to the strong bonds
Methylbenzene is … A polar molecule
Not
HCl won’t be formed in methylbenzene as…
It is not polar and so unable to break apart the hydrogen and chlorine
