chemical changes Flashcards
A strong acid is completely _______ in aqueous
solution.
ionised
A weak acid is only _______ ionised in aqueous
solution
partially
A weak acid (aq) has a lower pH than a strong acid (aq) of the same concentration. This is because ….
a weak acid has a lower concentration of hydrogen ions.
Metal + acid →
salt + hydrogen
Salts made when metals react with nitric acid are called ….
nitrates.
Salts made when metals react with sulfuric acids are called ….
sulfates.
Salts made when metals react with hydrochloric acid are called ….
chlorides.
Making Soluble Salts from acids and alkalis =
Acid + Alkali → Salt + Water
Making Soluble Salts from acids and bases =
Acid + Bases → Salt + Water
Making Soluble Salts from acids and metal carbonates =
Acid + Metal carbonate → Salt + Water + Carbon dioxide
what is a base?
Any substance that reacts with an acid to form a salt and water only.
The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns with a …..
pop sound.
The test for carbon dioxide uses an aq solution of calcium hydroxide (lime water). When carbon dioxide is shaken or bubbled through limewater the limewater turns ….
milky (cloudy)
1) Use the pipette to add 25 cm3 of alkali to a conical flask and add a few drops of indicator. 2) Fill the burette with acid and note the starting volume. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
3) Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading. Repeat steps 1 to 3 until you get consistent readings.
Soluble salts can be made from acids by reacting them with ….
solid insoluble substances
1) Measure the required volume of acid with a measuring cylinder and add the weighed solid (insoluble metal, oxide, hydroxide or carbonate) in small portions with stirring.
2) Safety goggles required - the mixture may be heated to speed up the reaction. When no more of the solid dissolves, it means ALL the acid is neutralised and there should be a little excess solid.
3) Filter the solution to remove the excess solid metal/oxide/carbonate into an evaporating dish. On filtration, only a solution of the salt is left.
4) Then hot concentrated solution is left to cool and crystallise.
5) After crystallisation, you collect and dry the crystals with a filter paper. If the solution is heated, the solvent will evaporate faster. Heating a solution until all the solvent has evaporated is known as heating to dryness.
Insoluble salts can be made from ….
two soluble salts.
