C4 chemical changes

Question 1

what happens when a metal and an oxygen react

Answer 1

they form a metal oxide

Question 2

reactivity of metals is related to what

Answer 2

there tendency to create positive ions

Question 3

what is the rule of displacement in metals

Answer 3

A more reactive metal can displace a less reactive metals from a compound

Question 4

where are the most reactive metals on the reactivity scale

Answer 4

the top

Question 5

what metals can be extracted from their compound by reduction

Answer 5

metals that are less reactive than carbon

Question 6

give the equation of an oxidised sodium (Na)

Answer 6

Na -> Na+ + e-

Question 7

if sodium +1 ion is reduced give the equation

Answer 7

Na+ + e- -> Na

Question 8

what is produced when an acid reacts with a metal

Answer 8

salt + hydrogen

Question 9

what is a redox reaction

Answer 9

a reaction between acid and metal where one substance is reduced and one is oxidised

Question 10

what is produced in a neutralisation reaction

Answer 10

salt and water

Question 11

what is made when acid reacts with metal carbonate

Answer 11

salt and water and carbon dioxide

Question 12

what does soluble mean

Answer 12

can dissolve

Question 13

what is titration

Answer 13

an experiment used to determine the amount of an acid or alkali to become neutral

Question 14

describe how to do a titration experiment

Answer 14

1. Fill burette with 100cm acid with the meniscus’ base on the 100cm3 line
2. Use 25cm3 pipette to add 25cm3 of alkali into a conical flask, drawing alkali into the pipette using a pipette filler
3. Add a few drops of a suitable indicator to the conical flask (eg: phenolphthalein which is pink when alkaline and colourless when acidic)
4. Add acid from burette to alkali until end-point is reached (as shown by indicator)
5. The titre (volume of acid needed to exactly neutralise the acid) is the difference between the first (100cm3) and second readings on the burette
6. Repeat the experiment to gain more precise results

Question 15

how do you work out the concentration of an acid

Answer 15

1. Convert volumes into dm3
2. Work out the moles of acid
   moles = volume x concentration
3. Work out mole ratio from equation
4. Work out concentration

Question 16

how many cm3 are there in 1 dm3

Answer 16

1dm3= 1000cm3

Question 17

what happens to strong acids in aqueous solution

Answer 17

they are completely ionised forming H+ ions

Question 18

what happens to weak acids in aqueous solutions

Answer 18

partially ionised forming H+ ions

Question 19

what happens as the PH decreases by 1

Answer 19

hydrogen concentration increases by 10

Question 20

what is electrolysis

Answer 20

passing current through a molten substance so the solution can be broken down into elements

Question 21

what is an electrolyte

Answer 21

the substance being broken down by electrolysis

Question 22

what metals are extracted using electrolysis (molten)

Answer 22

those that are more reactive than carbon

Question 23

what do aqueous solutions create at the cathode (negative electrode)

Answer 23

hydrogen unless the metal is
less reactive than hydrogen this is because more reactive ions want to stay within the solution

Question 24

what is produced at the anode (positive electrode)

Answer 24

At the positive electrode, if OH- and halide ions (Cl-, Br-, I-) are present, then one of the halide ions will be produced. If no halide is present, oxygen is formed.

Question 25

What ions do alkalis form in aqueous solutions?

Answer 25

OH- ions