chemical changes

Question 1

what is a titration

Answer 1

used to find unknown concentration of an acid or alkali

Question 2

equipment needed for titration

Answer 2

pipette
conical flask
burette
white tile

Question 3

titration practical
-use a …… to add ….. cm^3 of ……. to a clean ……. …… .
-add few drops of …. and put …… ….. on a ….. …..
-fill …… with ……. ….. and note starting volume
-slowly add the …. from the ….. to the …. in the …… ….., swirling to mix
-stop adding the ….. when the ….. changes color (when neutralised)
-note final reading, and calculate total volume of …. added.
-repeat until you get results that are 0.1 cm^3 of each other, then calculate mean

Answer 3

-pipette, 25, alkali, conical flask
-indicator, conical flask, white tile
-burette, sulfuric acid
-acid, burette, alkali, conical flask
-acid, indicator
-acid

Question 4

name an indicator to use in titrations

Answer 4

-methyl orange
-litmus
-phenolphthalein

Question 5

what is meniscus

Answer 5

the curve of a liquid when it touches a material

Question 6

convert cm to dm

Answer 6

/ by 1000

Question 7

how to calculate no. of moles

Answer 7

concentration x volume

Question 8

how to calc concentration

Answer 8

no. of moles/volume

Question 9

what is a redox reaction

Answer 9

a reaction where reduction and oxidation happen at the same time

Question 10

why use a pipette and why use a burette

Answer 10

pipette measures a fixed volume
(accurately)
(but) burette measures variable
volume

Question 11

what is an electrolyte

Answer 11

liquid or solution containing an ionic compound (ions are free to move)

Question 12

the right electrode is
the left electrode is

Answer 12

the left electrode is cathode -
the right electrode is anode +

Question 13

what does it mean when an ion gets discharged at an electrode

Answer 13

the atom goes from a charged ion to a neutral atom

Question 14

electrolysis is a process where

Answer 14

you can separate ionic compounds into their pure elements by passing an electric current through an electrolyte

Question 15

how to turn an aluminum oxide ore into molten aluminum oxide

Answer 15

• purify the ore
• mix with mineral cryolite (this lowers melting point)
• melt

Question 16

ionic equation for water

Answer 16

H^+ + OH^-

Question 17

which ion in an aqueous solution of electrolysis will get discharged on a cathode

Answer 17

the least reactive element

Question 18

which ion in an aqueous solution of electrolysis will get discharged on an anode

Answer 18

• if a halide is present (group 7) then that will be the one to get discharged
• else the hydroxide ion gets discharged

Question 19

Why do electrodes need to be constantly replaced

Answer 19

because o2 is formed which reacts with the C of the electrode forming co2 and gradually burns away

Question 20

an acid is a substance that forms

Answer 20

aqueous solutions of pH less than 7
because they ionise, to release H+ ions

Question 21

what is a strong acid

Answer 21

-an acid that ionises completely
-the reactants turn completely into products

Question 22

what is a weak acid

Answer 22

don’t fully ionise to release hydrogen ions
-ionisation of a weak acid is reversible

Question 23

what do metal hydroxides and oxide form when reacting w/ an acid

Answer 23

salt + water

Question 24

what do metal carbonates form when reacting with an acid

Answer 24

salt + water + carbon dioxide

Question 24

what do metal carbonates form when reacting with an acid

Answer 24

salt + water + carbon dioxide

Question 25

how to form a soluble salt using an acid and insoluble base

Answer 25

• put dilute acid in a beaker and gently heat w/ bunsen burner
• add to the insoluble base until it doesn’t dissolve
• the base is an excess and acid is now neutralized
• filter out the excess base
• heat solution to the evaporate some water
• when crystal start forming leave it to cool
• filter and dry the crystals

Question 26

To work out the formula of the salt,

Answer 26

take +ve ion from base, such as sodium from sodium oxide (Na2O), and -ve ion from acid, such as chloride from hydrochloric acid (HCl), and combine together