Chemical changes Flashcards
(39 cards)
Why does potassium react violently with water?
It is very reactive and easily loses its outer electron.
Why do calcium and magnesium react differently with water?
Calcium reacts slowly; magnesium needs hot water or steam.
How does the position in the reactivity series relate to electron loss?
Higher metals lose electrons more easily to form positive ions.
What determines if a displacement reaction occurs?
A more reactive metal must be above the other in the reactivity series.
Why doesn’t copper displace zinc from zinc sulfate?
Copper is less reactive than zinc.
Why can iron be extracted using carbon?
Iron is below carbon, so carbon can reduce its oxide.
Why is electrolysis used for aluminium extraction?
Aluminium is too reactive to be reduced by carbon.
Why is electrolysis more expensive than carbon reduction?
It uses large amounts of electricity.
What shows that a reaction between metal and acid is exothermic?
Temperature rises as energy is released forming bonds.
How does the salt name depend on the acid used?
Hydrochloric → chloride, sulfuric → sulfate, nitric → nitrate.
Why does magnesium react faster than iron with hydrochloric acid?
Magnesium is more reactive; it loses electrons more easily.
Why is water always a product in acid + base reactions?
H⁺ from acid reacts with OH⁻ from base to form water.
What is the ionic equation for neutralisation?
H⁺ + OH⁻ → H₂O.
Why is pH 7 the endpoint in strong acid + strong base titrations?
The solution is neutral; H⁺ and OH⁻ are equal.
Why is excess base added to acid when making salts?
To make sure all acid reacts and no acid remains.
Why is filtration used after base and acid react?
To remove the unreacted excess base.
Why is crystallisation used at the end of salt preparation?
To obtain pure salt by evaporating water.
Why does a strong acid conduct electricity better than a weak acid?
It has more free ions in solution.
How does strong vs weak acid affect reaction rate?
Stronger acids react faster due to more H⁺ ions.
Why do strong and weak acids of same concentration have different pH?
Stronger acids fully ionise, giving more H⁺ ions.
Why is carbon used in blast furnaces?
It reduces iron(III) oxide to molten iron.
Why does zinc displace iron from iron sulfate?
Zinc is more reactive and forms ions more easily.
Why does acid concentration affect the rate of hydrogen production?
Higher concentration means more H⁺ ions available to react.
How can you show that magnesium is more reactive than copper?
Magnesium displaces copper from copper sulfate.
