REACTIVITY SERIES [dchemlc]

What will be produced from the following displacement reaction?

Mg(s) + CuO(s) ----->

• MgO and Cu

• Nothing will happen

• Mg and Cu

• Cu and O₂

Answer explanation

The less reactive metal, copper, has been displaced from its compound by the more reactive magnesium. Any metal higher in the reactivity series will displace one lower down from a compound.

At the end, traces of white magnesium oxide are left on the ceramic paper.

Tags

NGSS.HS-PS1-2

Choose the most appropriate answer for the blanks (a) and (b) respectively

Oxidation is __________ of oxygen and reduction is ___________ of oxygen

• (a)gain (b) gain

• (a) loss (b) loss

• (a) gain (b) loss

• (a) loss (b) gain

Answer explanation

A substance has been oxidized if it gains oxygen. Oxidation is gain of oxygen.

A substance has been reduced if it loses oxygen. Reduction is loss of oxygen.

Tags

NGSS.HS-PS1-2

Choose the most appropriate answer for the blanks (a) and (b) respectively

Oxidation is __________ of electrons and reduction is ___________ of electrons

• (a)gain (b) gain

• (a) loss (b) loss

• (a) gain (b) loss

• (a) loss (b) gain

Answer explanation

• oxidation is loss of electrons • reduction is gain of electrons.

The mnemonic OILRIG can be helpful in remembering this:

Oxidation

Is

Loss of electrons

Reduction

Is

Gain of electrons

Tags

NGSS.HS-PS1-2

Choose the most appropriate answer for the blanks (a) and (b) respectively

The oxidizing agent always gets _____________ while the reducing agent always gets ____________

•  (a)reduced

  (b) reduced

• (a) oxidized

  (b) oxidized

• (a) oxidized

  (b) reduced

• (a) reduced

  (b) oxidized

Answer explanation

An oxidizing agent always gets reduced in a chemical reaction because it oxidizes something else by giving away its oxygen.

A reducing agent always gets oxidized in a chemical reaction because it takes the oxygen away from something else and therefore gains oxygen itself.

Tags

NGSS.HS-PS1-2

What is the color change of the solution in the following reaction?

Zn(s) + CuS0₄ (aq) ------> ZnSO₄ (aq) + Cu(s)

• Blue to colorless

• Colorless to blue

• No color changes.

• Blue to white

Answer explanation

The copper is displaced by the more reactive zinc. The blue colour of the copper(II) sulfate solution fades as colourless zinc sulfate solution is formed

Tags

NGSS.HS-PS1-2

Calcium reacts gently with cold water to give a white, insoluble solid which will very slightly dissolve in water to give a colorless solution and a colorless gas. Hence what are the products of the following reaction?

Ca(s) + 2H₂O(l)------>

• Ca(OH)₂

• O₂

• H₂

• CaO

Answer explanation

Calcium hydroxide is formed. This isn't very soluble in water. Some of it dissolves to give a colourless solution, but most of it is left as a white, insoluble solid.

Ca_(s) + 2H₂0_(l) ---------> Ca(OH)_{2(aq or s)} + H_2(g)

Tags

NGSS.HS-PS1-2

What is produced when magnesium is reacted with steam?

• H₂

• O₂

• MgO

• Mg(OH)₂

Answer explanation

The magnesium burns with a bright white flame in the steam, producing hydrogen, which can be ignited at the end of the delivery tube. White magnesium oxide is formed:

Mg(s) + H₂O(g) ------->MgO(s) + H₂(g)

Tags

NGSS.HS-PS1-2

Which of the following is needed for iron to rust?

• water

• oxygen

• hydrogen

• sulfuric acid

Answer explanation

Iron rusts in the presence of oxygen and water.

The formula of rust is

Fe₂0₃·xH₂0, where x is a variable number. It can be called 'hydrated iron (III) oxide'.

Rusting can be described as a redox reaction - the iron is oxidized.

Tags

NGSS.HS-PS1-2

Which of the following elements cannot be used to protect the metal hulls or keels of ships from rusting?

• zinc

• aluminium

• magnesium

• copper

Answer explanation

you have to use a metal that is more reactive than iron; the more reactive metal reacts (is oxidised) more readily in the presence of oxygen/water than the iron. The corrosion of the more reactive metal prevents the iron from rusting.

copper is less reactive than iron.

Tags

NGSS.HS-PS1-1

What are the products of the following reaction?

3Fe(s) + 4H₂0(g) ----->

• H₂

• O₂

• Fe₃O₄

• Fe₂O₃

Answer explanation

With both zinc and iron, the hydrogen comes off slowly enough to be collected. Neither metal burns.

The iron becomes slightly darker grey. A complicated oxide is formed, called tri-iron tetroxide,

3Fe(s) + 4H₂0(g) -----------> Fe₃O₄(s) + 4H₂(g)

Tags

NGSS.HS-PS1-2