Chemical Changes 1+2 Flashcards
what are the three most common acids?
- hydrochloric acid (HCl)
- Sulfuric acid (H2SO4)
- nitric acid (HNO3)
Types of salt that can form from the acids
- nitrate
- chloride
- sulfate
What can salts be used for?
- seasoning food
- dissolved in drinking water
- perserve food
- fertilizers (sulfate and nitrate salts)
What kind of reaction is the reaction between acids and metals?
- redox reaction
- (oxidation and reduction reaction taking place at the same time)
What is oxidation?
- gain of oxygen or losing of electrons of a substance in a reacton
What is reduction?
- losing of oxygen, gaining of electrons or gaining hydrogen by a substance in a reaction
what do all acids have?
hydrogen ions
What is the difference between an alkali and a base?
- alkalis are soluble, they can dissolve in water
- all alkalis are bases but not all bases are alkali
How do you identify a base?
- name ends with carbonate or oxide
How do you identify an alkali?
- if the metal is in group 1/2 ending with hydroxide
How do you identify a salt?
- ends with sulfate/ nitrate/ chloride
compound ions names
- hydroxide (OH-)
- nitrate ion (NO3-)
- sulfate ion (SO4 2-)
- carbonate ion (CO3 2-)
What is neutralisation?
When acids are neutralised by alkalis and bases to produce salt and water, and by metal carbonates to produce salts, water and carbon dioxide
What does alkalis and bases produce when they neutralise acids?
Water and salt
What do metal carbonates produce when they react with acid?
Salt, water, and carbon dioxide
What salt does the three most common acids make
Hydrochloric acid - chloride
Sulfuric acid - sulfate
Nitric acid - nitrite
How do you make pure, dry samples of soluble salts?
- measure acid using measuring cylinder and pour it into beaker
- gently heat the acid by placing it on a bunsen burner and a tripod (speeds up reaction)
- take acid off bunsen and add spatulas of the alkali/ base until the powder at the bottom of the beaker. (to make sure that the alkali/ base is in excess) the solution should turn into a different colour (blue for copper sulfate)
- remove the excess copper oxide by filtering it using a funnel and filtering paper (to remove excess copper oxide)
- pour the solution into evaporating basin and heat over a beaker of boiling water(if the solution is heated directly the crystals will break down)
- take evaporating basin off the water bath once half of the solution is gone and leave it out at room temp to let it evaporate naturally (larger crystals can form)
- after water has evaporated entirely, put crystals on filiter paper (to make sure that it is completely dry)
Why do we not use an oven to dry out the crystals?
- the cyrstals would turn into powder
- removes the water molecules from the crystal (needs water to remain crystal)
describe the colour of universal indicator from acid to alkali
acid - red, orange, yellow
neutral - green
alkali - blue, purple
what are strong acids in an aqueous solution?
completely ionised
what are weak acids in an aqueous solution?
partially ionised
how much does the concentration of hydrogen ions need to be diluted by to increase the pH by 1?
10 times, the less hydrogen ions, the higher the pH
Write a half equation of sodium for the reduction of sodium ions
2Na -> 2Na+ + 2e-
Write a half equation for the reduction of chloride ions
Cl2 + 2e -> 2Cl-
What is given off when a metal reacts with water or acid and what can react with them?
- hydrogen gas
- metals > hydrogen in reactivity can react with dilute acids
How do displacement reactions work?
- more reactive metal displaces less reactive metal from compound
How are unreactive metals (gold, silver, platinum etc) found?
- in the earth’s crust
- as pure metals
- mined
How are metals that are less reactive than carbon extracted?
- found as ores
- heating with carbon
- reduction
How are metals that are more reactive than carbon extracted?
eg. aluminium
- electrolysis
Steps for writing an ionic equation
1) check symbol equation is balanced
2) identify all aqueous ionic compounds
3) write those compounds out as ions
4) remove spectator ions
What can be used to show pH?
- universal indicator
- electronic pH probes (gives exact pH)
What is the reactivity of a metal?
- its tendency to form positive ions
What do metals produce when they react with oxygen and what reaction is it?
- metal oxides
- oxidation, metal gains oxygen
What do reactive metals do when they react with oxygen?
- burn with a flame
- eg. magnesium
What do unreactive metals do when they react with oxygen?
- they tarnish and change colour without a flame
- eg iron
What do potassium, sodium and lithium do when they react with acid?
- they explode
- produce hydrogen gas
- reacts more vigorously
What do calcium, magnesium, zinc and iron do when they react with acid?
- they fizz and give off hydrogen gas
What does copper do when it reacts with acid?
- no reaction
What happens when potassium, sodium, lithium, and calcium do when they react with water?
- they fizz and give off hydrogen gas
What do magnesium and zinc do when they react with water?
- they react very slowly
What happens when copper reacts with water?
- no reaction
How are metal oxides that are less reactive than carbon extracted?
- by reduction with carbon
- produces carbon dioxide
