halogens [ dchemlc]

1. Which of the following is a solid at room temperature?

• Cl₂

• Br₂

• Fl₂

• I₂

Answer explanation

iodine is a grey solid but has a purple vapor.

2. What color is chlorine gas at room temperature?

• green

• yellow

• colorless

• brown

Answer explanation

don't forget chlorine is a green gas! :)

3. Which of the following elements do not have 7 electrons in its last shell?

• flourine

• astatine

• iodine

• xenon

Answer explanation

xenon is an ideal gas silly :)

it belongs to group 8

4. select the correct answer for (a) and (b) respectively

The melting and boiling points of halogens (a)_______________ down the group and the reactivity of halogens (b) ____________ down the group

• (a) increase

  (b)increase

• (a)decrease

  (b) decrease

• (a) increase

  (b) decrease

• (a) decrease

  (b) increase

Answer explanation

now do you know why reactivity decreases and melting points and boiling points increases?

5. fill in the blank

Halogens are ____________ conductors of heat and electricity.

• poor

• strong

Answer explanation

halogens are non metals

therefore they are poor conductors of heat and electricity.

6. what will be produced by the reaction between hydrogen and a halogen?

• hydrogen sulfide

• hydrogen halide

• hydrogen carbonate

• hydrogen oxide

Answer explanation

these hydrogen halides are acidic, poisonous gases.

7. what will be produced in the following reaction?

 H₂O_(l) + HF_(g)-------->

• Oxygen and fluorine

• hydrofluoric acid

• Hydrochloric acid

• Fluorine and water

Answer explanation

hydrogen halides dissolve in water to give solutions of acids.

e.g. hydrochloric acid

hydrobromic acid

hydroiodic acid

8. what is the color change when chlorine water is added to a solution of potassium bromide?

• color stays the same

• colorless to orange

• orange to colorless

• orange to brown

Answer explanation

bromine is formed because chlorine is more reactive than bromine and displaces it

Cl₂ + KBr-----> KCl + Br₂

potassium bromide is colourless

bromine gives an orange colour

hence the colour change

9. what will be produced in the following reaction?

KI + Br₂ ------>

• KIBr

• No reaction

• KBr + I₂

• K₂O + I₂

Answer explanation

the more reactive bromine displaces the less reactive iodine from potassium iodide solution. iodine is produced

colour changes from colourless to brown

10. what will be produced in the following reaction?

I₂ + KCl ----->

• no reaction

• KI + Cl₂

• K₂O + Cl₂

• KICl

Answer explanation

the less reactive iodine cannot replace the more reactive chlorine.