CHEMISTRY - Acids, Bases and Salts Flashcards
how does the pH scale work
ph 0-2 is red
ph 3-4 is orange
pg 5-6 is yellow
7 is green
8-9 is blue
10-12 is navy blue
13-14 is purple
0-6 is acid
7 is neutral
8-14 is alkali
what is the main difference between acids and alkalis
acids are a source of H+ ions
alkalis are a source of OH- ions
the stronger the acid, the more H+ ions
same for alkalis but with OH- ions
what are the 4 things than we can see when a chemical reaction has taken place
- temperature change
- colour change
- bubbles/effervescing
- precipitate
(i said pH change so yes allow that one)
what does exothermic mean
when heat EXITS the experiment and the temperature increases
if you dont get it
the heat exits so you feel it, so its when the temp increases
EX - othermic
ex for exit
what does endothermic mean
opposite of exothermic
EN-dothermid, heat ENTERS the experiment and temperature decreases
give two example for an exothermic reaction
-combustion
-respiration (opposite of photosynthesis which is endothermic)
give two examples for endothermic reactions
-thermal decomposition
-photosynthesis (opposite of respiration which is exothermic)
when metals react with acids, which gas is given off
hydrogen
how do we test for hydrogen
place a lit splint into a tube with the gas, and it will burn with a squeaky pop if the gas is hydrogen
there is a type of reaction called neutralisation, explain it.
give two examples.
when an acid reacts with a base, they cancel each other out, product of this reaction is neutral, hence it is called neutralisation.
eg 1. wasp sting is alkali, so using lemon juice which is acid will neutralise it.
eg 2. bee sting is acidic, so toothpaste can neutralise it because its an alkali
what equation is generally used when an acid reacts with an alkali or base?
acid with alkali =
acid + alkali –> salt + water
acid with base =
acid + base —> salt + water
in a neutralisation reaction what happens with the hydrogen and hydroxide ions (H+ and OH- ions)
and what equation shows this.
the H+ ions from the acid and the OH- ions from the alkali will react to form water
shown by the equation
H+ + OH- —> H2O
and H2O is water
whats the difference between bases and alkalis
base tends to be oxide
alkali tends to be hydroxide
what can be observed when an acid reacts with a carbonate
fizzing/bubbling/does effervescing count?
what is the test for CO2 (carbon dioxide)
when you mix calcium carbonate with hydrochloric acid and if the reaction produces bubbles and turns milky, then it means CO2 is produced.
