4.2 - group 1 and 7

Question 1

explain the trend in reactivity down group 1

Answer 1

• down group one, the number of shells increase
• distance between electron being removed and nucleus increases
• therefore attraction between outer electron and nucleus decreases
• therefore easier to remove the electron

Question 2

define an acid

Answer 2

H+ donor

Question 3

define an alkali

Answer 3

OH- donor

Question 4

When metals reacts with oxygen, what is produced? Will this compound produce an acid or alkaline solution when dissolved in water?

Answer 4

metal oxide => alkaline solution

Question 5

describe what would be seen when magnesium reacts with oxygen

Answer 5

• bright white light
• white solid formed

Question 6

describe what would be seen when sulphur reacts with oxygen

Answer 6

blue flame

Question 7

After the reaction of potassium with water is complete a few drops of universal indicator are added to the solution formed, the universal indicator turns purple. Give the formula of the ion responsible for this pH value.

Answer 7

OH-

(because it is alkaline and alkaline is an OH- donor)

Question 8

explain why lithium is less reactive than sodium

Answer 8

• lithium has less shells than sodium
• therefore outer electron is closer to nucleus
• therefore attraction between nucleus and electron is greater
• therefore harder to lose electron

Question 9

Sodium can react with oxygen form sodium oxide. Sodium oxide has a very high melting point — explain why.

Answer 9

• giant ionic lattice
• strong electrostatic attraction between positive and negative ions
• therefore requires a lot of energy to overcome

Question 10

what is fluorine‘s appearance at room temperature?

Answer 10

pale yellow gas

Question 11

what is chlorine‘s appearance at room temperature?

Answer 11

green gas

Question 12

what is bromine‘s appearance at room temperature?

Answer 12

brown(/red) liquid

Question 13

what is iodine‘s appearance at room temperature?

Answer 13

grey solid

Question 14

what is astatine‘s appearance at room temperature?

Answer 14

black solid

Question 15

what happens to the appearance of the group 7 elements at room temperature as they go down the table

Answer 15

they become DARKER - “more solid”

Question 16

what is fluorine‘s reaction with iron wool?

Answer 16

too dangerous/reactive to do

Question 17

what is chlorine‘s reaction with iron wool?

Answer 17

minimal heating (needed)
iron glows brightly

Question 18

what is bromine‘s reaction with iron wool?

Answer 18

more heating (needed)
iron glows less brightly

Question 19

what is iodine‘s reaction with iron wool?

Answer 19

strong heating (nee)
iron has a small amount of glowing

Question 20

what is astatine‘s reaction with iron wool?

Answer 20

very strong heating

Question 21

what happens to the reactivity of the group 7 elements as they go down the group

Answer 21

it decreases

Question 22

explain why the reactivity decreases down group 7 (speak about fluorine and chlorine)

Answer 22

• both need to gain 1 electron
• chlorine has more shells than fluorine
• Incoming electron is further from the nucleus
• weaker attraction between electron and nucleus therefore harder to gain

Question 23

what do all diatomic elements elements need when written in an equation

Answer 23

(X)₂

X being the element

Question 24

what is the chemical test for oxygen

Answer 24

• put GLOWING splint into gas
• if splint reignites, oxygen is present

Question 25

what is the chemical test for carbon dioxide

Answer 25

- bubble gas into lime water - turns cloudy white if carbon dioxide is present

Question 26

what is the chemical test for hydrogen

Answer 26

- put lit splint into gas - squeaky pop sound if hydrogen is present

Question 27

what is the chemical test for water

Answer 27

- add ANHYDROUS COPPER SULPHATE to water - turns white -> blue if water is present

Question 28

what is the purity test for water

Answer 28

- boil/freeze water - boil - 100°C if pure - freeze - 0°C if pure

Question 29

what is the chemical test for chlorine

Answer 29

- DAMP BLUE litmus paper into gas - turns white/bleaches (think washed blue jeans - blue jeans = blue litmus paper, washed = bleaches/white)

Question 30

which halogen has the palest colour?

Answer 30

fluorine

Question 31

which halogen is a solid at room temperature?

Answer 31

astatine

Question 32

explain the relative reactivities of fluorine and chlorine using the information in the table: electronic configuration - fluorine - 2.7 chlorine - 2.8.7

Answer 32

- both need to gain 1 electron - chlorine has more shells than fluorine - incoming electron is further from the nucleus - That will attraction is weaker - Therefore harder to gain electron - therefore less reactive