Reactivity of Metals Flashcards

All 34 cards in this deck

What is produced when a metal reacts with oxygen?

A metal oxide.
e.g. magnesium + oxygen → magnesium oxide

Why is the reaction of a metal with oxygen classed as oxidation?

Because the metal gains oxygen.

Define oxidation and reduction in terms of oxygen.

Oxidation is the gain of oxygen; reduction is the loss of oxygen.

What is the balanced symbol equation for magnesium burning in oxygen?

$2\mathrm{Mg} + \mathrm{O_2} \rightarrow 2\mathrm{MgO}$

What are the steps to write a balanced symbol equation for a metal reacting with oxygen?

e.g. copper reacting with oxygen

1. Write the word equation: copper + oxygen → copper oxide
2. Write formulae, remembering oxygen is $\mathrm{O_2}$: $\mathrm{Cu} + \mathrm{O_2} \rightarrow \mathrm{CuO}$
3. Balance the atoms: $2\mathrm{Cu} + \mathrm{O_2} \rightarrow 2\mathrm{CuO}$

True or false? In the reaction $2\mathrm{Mg} + \mathrm{O_2} \rightarrow 2\mathrm{MgO}$, the magnesium is reduced.

False. Magnesium gains oxygen, so magnesium is oxidised.

What is the reactivity series?

A list of metals arranged in order of their reactivity, from most reactive to least reactive.

State the order of reactivity of potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper, most reactive first.

Potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper.

Which two non-metals are often included in the reactivity series, and where do they sit?

Carbon (between aluminium and zinc) and hydrogen (between iron and copper).

What does the reactivity of a metal depend on, in terms of ions?

Its tendency to form positive ions — the more easily it loses electrons to form its positive ion, the more reactive it is.

Which of potassium, sodium, lithium and calcium react with cold water, and what is formed?

All of them react with cold water, forming a metal hydroxide and hydrogen.

Give two observations when a small piece of potassium is added to cold water.

Any two: it floats, melts, moves around, gets smaller, effervescence, a (lilac) flame.

Which of magnesium, zinc, iron and copper react with dilute acid at room temperature?

Magnesium, zinc and iron react (magnesium fastest, iron slowest); copper does not react.

True or false? Copper does not react with dilute acid because it is below hydrogen in the reactivity series.

True. Copper cannot displace hydrogen from the acid.

How can you deduce an order of reactivity for metals from their reactions with dilute acid?

e.g. three metals each added to hydrochloric acid

1. Compare the rate of effervescence: the faster the bubbles, the more reactive.
2. Compare the temperature rise: the bigger the rise, the more reactive.
3. Any metal showing no reaction is the least reactive.

Why is calcium more reactive than magnesium?

Calcium's outer electrons are further from the nucleus and less strongly attracted, so it loses electrons and forms its positive ion more easily.

What happens when a more reactive metal is added to a solution of a less reactive metal's salt?

The more reactive metal displaces the less reactive metal from the compound.
e.g. zinc + copper sulfate → zinc sulfate + copper

True or false? A less reactive metal can displace a more reactive metal from its salt solution.

False. Only a more reactive metal can displace a less reactive one.

In what form are unreactive metals such as gold found in the Earth?

As the metal itself (uncombined/native), because they are so unreactive.

Which metals can be extracted from their oxides by reduction with carbon?

Metals less reactive than carbon.
e.g. zinc, iron, copper

What is meant by reduction in a metal extraction reaction?

Loss of oxygen from a substance.

In $2\mathrm{Fe_2O_3} + 3\mathrm{C} \rightarrow 4\mathrm{Fe} + 3\mathrm{CO_2}$, which substance is reduced and which is oxidised?

$\mathrm{Fe_2O_3}$ is reduced because it loses oxygen; carbon is oxidised because it gains oxygen.

How do you decide whether a metal can be extracted by reduction with carbon?

e.g. zinc oxide

1. Find the metal's position in the reactivity series relative to carbon: zinc is below carbon.
2. If it is below carbon, carbon can reduce (displace it from) its oxide: yes for zinc.
3. If it is above carbon, electrolysis must be used instead.

True or false? Most metals are found in the Earth as compounds that need a chemical reaction to extract the metal.

True. Only very unreactive metals such as gold are found as the metal itself.

Why is it a problem to use magnesium rather than carbon to reduce silicon dioxide ($2\mathrm{Mg} + \mathrm{SiO_2} \rightarrow \mathrm{Si} + 2\mathrm{MgO}$)?

Both products are solids, so they are difficult to separate.

Define oxidation and reduction in terms of electrons.

Oxidation is the loss of electrons; reduction is the gain of electrons.

In a displacement reaction between a metal and a metal ion in solution, which species is oxidised?

The metal atom, because it loses electrons to form its positive ion.
e.g. $\mathrm{Mg} \rightarrow \mathrm{Mg^{2+}} + 2e^-$

What is a redox reaction?

A reaction in which oxidation and reduction happen at the same time (one species loses electrons as another gains them).

What are the steps to write the ionic equation for a displacement reaction?

e.g. zinc added to copper sulfate solution

1. Write the full equation: $\mathrm{Zn} + \mathrm{CuSO_4} \rightarrow \mathrm{ZnSO_4} + \mathrm{Cu}$
2. Cross out the spectator ion ($\mathrm{SO_4^{2-}}$, unchanged on both sides).
3. Write what is left with state symbols: $\mathrm{Zn(s)} + \mathrm{Cu^{2+}(aq)} \rightarrow \mathrm{Zn^{2+}(aq)} + \mathrm{Cu(s)}$

In $\mathrm{Mg(s)} + \mathrm{Zn^{2+}(aq)} \rightarrow \mathrm{Mg^{2+}(aq)} + \mathrm{Zn(s)}$, which species is oxidised and which is reduced?

Magnesium atoms are oxidised (lose electrons); zinc ions are reduced (gain electrons).

True or false? Oxidation can only happen if oxygen is involved.

False. Oxidation is the loss of electrons, which can happen with no oxygen present.

What is the half equation for the oxidation of zinc atoms?

$\mathrm{Zn} \rightarrow \mathrm{Zn^{2+}} + 2e^-$

When copper is added to silver nitrate solution, what two observations show a displacement reaction has happened?

Pale grey crystals of silver form and the solution turns blue (copper ions).

In an investigation comparing metals by measuring the temperature change when each is added to a solution, what shows that a metal is more reactive?

The greater the temperature change, the more reactive the metal.