PARTICULATE NATURE OF MATTER AND CHEMICAL CHANGE

Which equation correctly describes the reaction that occurs when sodium metal is added to water at room temperature?

• 2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

• Na_(s) + H₂O_(l) → NaOH_(s) + H_2(g)

• 2Na_(s) + 2H₂O_(aq) → 2NaOH_(aq) + H_2(g)

• 2Na_(s) + 2H₂O_(aq) → 2NaOH_(s) + H_2(g)

Which of the following are homogenous mixtures?

I. solid steel

II. an aqueous solution of salt

III. molten salt

• I and II only

• I and III only

• II and III only

• I, II and III

Sodium is a metal and chlorine is a green non-metal. They react together to form sodium chloride, NaCl. What can be deduced correctly about the physical properties of solid sodium chloride?

• It will conduct electricity .

• It will be a semi-metal (metalloid).

• Its melting point will be different to the melting points of sodium and chlorine.

• It will be green.

Which of the following is an element?

• air

• methane

• ozone

• ice

Which mixture can best be separated into its separate components by using chromatography?

• sodium hydroxide solution

• sea-water

• air

• black ink

Which reaction involves precipitation?

• AgNO_3(aq) + NaCl_(aq) → AgCl_(s) + NaNO_3(aq)

• NaOH_(aq) + H₂SO_4(aq) → Na₂SO_4(aq) + H₂O_(l)

• CaCO_3(s) + 2HCl_(aq) → CaCl_2(aq) + H₂O_(l) + CO_2(g)

• Fe_(s) + S_(s) → FeS_(s)

What is the sum of all the coefficients when the equation for the combustion of ethanol is balanced using the smallest possible whole numbers?

−C₂H₅OH_(l) + −O_2(g) → −CO_2(g) + −H₂O_(l)

• 9

• 9.5

• 19

• 8

Argon, carbon dioxide, oxygen and nitrogen are all present in air. What is the order in which the gases will be formed when liquid air is slowly warmed?

• N₂> Ar > O₂> CO₂

• CO₂> Ar > O_2> N₂

• N₂> O₂> Ar > CO₂

• CO₂ > O₂> Ar > N₂

At high altitude snow can sublime. Which statement correctly describes this process?

• Snow turns into liquid water.

• Snow forms hard ice.

• Snow turns into liquid water which then turns into water vapour.

• Snow turns directly into water vapour.

Which is the correct order for the coefficients in the balanced equation for the reaction between ammonia and oxygen to form nitrogen oxide and water. −NH_{3(g) +} −O_2(g) → −NO_(g) + −H₂O_(g) ?

• 4, 5, 4, 6

• 2, 3, 2, 3

• 2, 2, 2, 3

• 4, 7, 4, 6