SC8 - acids and alkalis

Question 1

what is there a high concentration of in acids

Answer 1

hydrogen (H+)

Question 2

what is there a high concentration of in alkalis

Answer 2

hydroxide (OH-)

Question 3

what is present in a neutral solution

Answer 3

equal amounts of H+ and OH-

Question 4

what colour is litmus paper in acids and alkalis

Answer 4

alkali- blue
acid-red

Question 5

what colour is methyl orange in acid and alkali

Answer 5

alkali- yellow
acid - red

Question 6

what colour is phenolphthalein in acid and alkali

Answer 6

alkali-pink
acid- colourless

Question 7

what is an ion

Answer 7

charged particle formed through gaining or losing electrons

Question 8

how do you work out concentration

Answer 8

amount dissolved/ volume of solution
given in g dm^-3

Question 9

what does ph measure

Answer 9

the concentration of hydrogen / H+ ions

Question 10

what is one dm^3 equal to

Answer 10

1000 cm ^3

Question 11

what happens to weak and strong acids in solutions

Answer 11

strong acid - molecules dissociate completly into ions when they dissolve in water which produces high concentrations of hydrogen ions

weak acids- they do not dissociate completly into ions in a solution so there are fewer hydrogen ions

Question 12

what is a base

Answer 12

substances which neutralise acids to form a salt and water only
all metal oxides are bases

base+ acid = salt and water

different acids form different salts

Question 13

what happens during neutralisation

Answer 13

hydrogen ios in the acid combine with oxide ions to form water , this removes the hydrogen ions and so the ph increaces (becomes more neutral)

H+ + OH- = H2O
the salts are produced by replacing the hydrogen ions with metal ions

the mixture can become warmer

Question 14

what are the endings for the 4 different types of salt

Answer 14

hydrocloric acid - chloride
nitric acid- nitrate
sulfuric acid- sulfate
ethanoic acid- ethonote

Question 15

how do you prepare a soluble salt

Answer 15

the reaction between an insoluble metal oxide and an acid can be used to produce insoluble salts
an excess of base was always used to make sure all the acid is used up
the salt is filtered to make sure it is pure to remove any residue
a solid sample is then extracted by crystillisation

Question 16

name the 6 chemical symbols you need to know

Answer 16

hydroxide- OH-
sulfate - So4 ^2-
nitrate - NO^3-
carbonate- CO3 ^2-
sulfite- SO3^2-
ammonium- NH ^4+

Question 17

how can titration be used to produce soluble salts

Answer 17

-it is important to have a neutral solution or you will be contaminating the salt with an excess of one reactant
-you need to mix the acid and alkali in correct proportions so only water and the salt are left
- this can be done through titiration

Question 18

what is the process of titration

Answer 18

• the end point is when the indicator changes colour
• use single indicators as it gives you a sharp end point
• after titration is carried out use the correct volume of acid needed and then evaporate the salt

Question 19

what happens when an acid reacts with a metal

Answer 19

metal + acid = salt + hydrogen

effervesence is seen as hydrogen gas bubbles are produced