Topic 4 - Chemical Changes Flashcards
How long is the pH scale and what side is acidic
0 - 14
0 - 6 is acidic
8 - 14 are alkaline
7 is neutral
What is a base
This is a substance with a pH greater than 7 (an alkali)
What is a neutralisation reaction and what is produced
When an acid and base react. The products are neutral
Acid + base –> salt water
e.g
hydrochloric acid + sodium oxide -> sodium chloride + water
What is the difference between weak and strong acids
When reacting with water, strong acids completely ionise whilst weak acids only partly ionise
When weak acids ionise, it is a reversible reaction
Stronger acids are more reactive due to more H+ ions
What is the difference between strong acids and concentrated acids
Acid strength is what proportion of acid molecules ionise in water
The concentration is how much acid there is in a certain volume of water
What is the pH scale a measure of and what is the scale
It is a measure of the concentration of H+ ions in the solution
It increases or decreases at each stage by a factor of 10
For example, an acid of ph 3 has 10x more H+ ions than an acid of ph 4
what is the formula/ general rule for changes of ph and hydrogen ions
(X is the amount of levels of ph are changed e.g 2)
Factor H+ ion concentration changes by = 10 to the power of X
what are metal oxides, metal carbonates metal hydroxides ( in terms of bases and acids) and what does this mean
They are bases, so all metal oxides and hydroxides will react with acids in neutralisation reactions to make a salt and water
but metal carbonates produce something different
What happens when acids and metal carbonates react
They produce salt, water and carbon dioxide
(So basically the same as neutralisation reactions, but they also produce CO2)
e.g
hydrochloric acid + sodium carbonate -> sodium chloride + water + carbon dioxide
What happens in the required practical that mixes an insoluble base and an acid
Heat up the dilute acid with a bunsen burner, then turn the bunsen burner off
place the insoluble base in the acid a bit at a time
filter out the excess solid to get the salt solution
Evaporate the water by heating it up, and leave to cool. The salt crystals will form, which is called crystallisation
What is crystallisation
This is when crystals of salt form and are filtered out of the solution and dried
Give the order of all 10 metals in the reactivity series (From most reactive at top to least at bottom)
(There are also two non metals in there as well
Very reactive metals: Potassium, K Sodium, Na Lithium, Li Calcium, Ca Fairly reactive metals: Magnesium, Mg Carbon, C Zinc, Zn Iron, Fe Not very reactive metals: Hydrogen, H Copper, Cu
What can the way that metals react with acids tell you
1.What is produced as well and 2.how can you tell the speed of the reaction
How the metals react tells you about their reactivity
The more reactive the metal is, the faster the reaction will go.
1.Acid + metal = Salt + Hydrogen
2. The rate that bubbles are given off shows the speed of the reaction
As well as this, the greater the temperature change is, the more reactive the metal is
What does metals reacting with water tell you
More reactive metals such as potassium, sodium lithium and calcium will react, whilst less reactive metals such as zinc and iron will not react with water
What is an Oxidation reaction
This is when an element, such as magnesium, gains oxygen to become oxidised e.g 2Mg + O2 = 2MgO
