Chemical reaction Flashcards by A A

\define oxidation (in terms of electrons)

Oxidation is the loss of electrons

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define reduction (in terms of electrons)

reduction is the gain of
electrons

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Mg —-> Mg2+ + 2e-

Describe what has happened

Magnesium, loses two electrons to form the Magnesium ion (mg2+ ion)

The magnesium atom has been oxidised as it has lost electrons

This is a oxidation reaction because the magnesium atom has lost electrons

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S + 2e- —> S2-

Describe what has happened

Sulfur has gained two electrons and formed the sulfide ion

The sulfur atom has been reduced as it has gained electrons

This is a reduction reaction has the sulfur atom has gained electrons

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OIL RIG

Oxidation is loss of electrons
Reduction is gain of electrons

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Identify in the reaction below which element (species) has been oxidised and which has been reduced

zinc + copper sulfate –> zinc sulfate + copper

Zn + CuSO4 –> ZnSO4 + Cu

The zinc atom has been oxidised as it has lost two electrons (oxidation is loss of electrons)

The copper ion has been reduced as it has gained two electrons (reduction is gain of electrons)

(We start with the zinc atom, Zn and we end up with the Zinc ion , Zn2+
In order for this to happen, the zinc atom must have lost two electrons, therefore the zinc atom has been oxidised.

We start with the copper ion, Cu2+ and end up with the copper atom, Cu. In order for this to happen, the copper must have gained two electrons, therefore it has been reduced.

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zinc + copper sulfate –> zinc sulfate + copper

Zn + CuSO4 –> ZnSO4 + Cu

what type of reaction is this

a displacement reaction

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write ionic equations for displacement reactions

Zn + CuSO4 –> ZnSO4 + Cu

Zn + Cu2+ + SO42- —> Zn2+ A-SO42- + Cu

Zn + Cu2+ —–> Zn2+ + Cu

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aq meaning

aq = aqueous solution - dissolved in water

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What do acids produce in aqueous solutions

In aqueous solutions, acids produce hydrogen ions (H+ ions)

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Write an equation to show how hydrochloric acid ionises in water
(showing hydrochloric acid in aqueous solution)

HCl (aq) –> H+(aq) + Cl- (aq)

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Describe what has happened
HCl (aq) –> H+(aq) + Cl- (aq)

This is how hydrochloric acid ionises in water

The molecule has split and released H+ (hydrogen ion)
The chloride ion (Cl-) has also been made (produced)

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Write an equation to show how sulphuric acid ionises in water
(showing sulfuric acid in aqueous solution)

And describe what has happened

H2SO4(aq) –> 2H+(aq) + SO42-(aq)

This is how sulfuric acid ionises in water

The molecule has split and released H+ (hydrogen ion)
The sulfate ion (SO42-) has also been made (produced)

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Write an equation to show how nitric acid ionises in water
(showing nitric acid in aqueous solution)

And describe what has happened

HNO3(aq) —> H+(aq) NO3-(aq)

This is how nitric acid ionises in water

The molecule has split and released H+ (hydrogen ion)

The nitrate ion (NO3-) has also been made (produced)

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What is an acid

A substance that releases H+ ions when in a solution

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What is a base

Chemicals which can neutralise acids producing a salt and water

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Examples of bases

Metal oxides
Metal hydroxides

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Examples of bases

Copper oxide
Iron (III) hydroxide
Sodium hydroxide

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Explain why Copper oxide
Iron (III) hydroxide and Sodium hydroxide are bases (are called bases)

All of these are bases because they can neutralise acids producing a salt and water

What is an alkali

Bases which are soluble in water are called alkalis

Out of Copper oxide
Iron (III) hydroxide
Sodium hydroxide

which ones are bases only and which ones are a base and an alkali.
Explain your choices

Copper oxide and Iron (III) hydroxide are both insoluble in water, so these are bases only

Sodium Hydroxide is soluble in water, so sodium hydroxide is both a base and an alkali

What do alkalis produce in aqueous solutions

In aqueous solutions, alkalis produce hydroxide ions (OH- ions) –

(alkalis are substances that release OH- ions when added to water)

Write an equation to show how sodium hydroxide ionises in water
(showing sodium hydroxide in aqueous solution)

And describe what has happened

NaOH(aq) –> Na+ (aq) + OH- (aq)

The sodium hydroxide is splitting, producing the sodium ion Na+ and the hydroxide ion OH-

The molecule has split and released OH- (hydroxide ion)
The Na+ (sodium ion) has also been made (produced)

What is the pH scale

The pH scale, from 0 to 14, is a measure of the acidity or alkalinity
of a solution,

What does the pH scale measure

The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution,

What pH's do acids, neutral solutions and alkalis have have

Acids have a pH between 0 and 6 Solutions with a pH of 7 are neutral Alkaline solutions have a pH between 8 and 14

How can you determine the pH of a solution (how can the pH of a solution be measured)

We can determine the pH of a solution using either a pH probe or Universal Indicator

How does a pH probe work

A pH probe determines the pH electronically

How does Universal Indicator work

Universal indicator changes colour, depending on whether a solution is acid, alkali or neutral (red, orange, yellow - acid) green -neutral blue, purple (alkali) increasing in numbers yellow - weak acid blue - weak alkali red - strong acid purple - strong alkali

What does the different colours of the Universal Indicator show

They show whether a solution is acid, alkali or neutral Green shows a neutral solution (pH 7) Very acidic solutions produce a red colour A purple colour shows a very alkaline solution

General equation for neutralisation

Acid + Alkali --> Salt + Water

Describe what happens during neutralisation

In neutralisation reactions, when an acid reacts with an alkali, the hydrogen ions react with the hydroxide ions to produce water

Write the (ionic) equation for neutralisation

H+ (aq) + OH- (aq) ---> H2O (l)

write the ionic equation for the reaction between hydrochloric acid and sodium hydroxide explain you choice

The reaction between hydrochloric acid and sodium hydroxide is a neutralisation reaction The ionic equation for a neutralisation reaction is H+ (aq) + OH- (aq) ---> H2O (l) therefore the ionic equation for the reaction between HCL and NaOH is also H+ (aq) + OH- (aq) ---> H2O (l)

H+ (aq) + OH- (aq) ---> H2O (l) explain this

In neutralisation reactions, when an acid reacts with an alkali, the hydrogen ions react with the hydroxide ions to produce water H+ ions from the acid OH- ions from the alkali

What can metals such as potassium, sodium, zinc etc. do to hydrochloric acid

These metals are more reactive than hydrogen Therefore they can displace hydrogen from acids

is this a displacement reaction explain why H2SO4 + Mg ---> MgSO4 + H2

sulfuric acid + magnesium --> magnesium sulphate + hydrogen Yes, it is a displacement reaction. In a displacement reaction, a more reactive element will displace (takes the place of) a less reactive element from its compound The magnesium is more reactive than the hydrogen, so it has displaced the hydrogen from the sulfuric acid

Explain why there is no reaction between copper and hydrochloric acid

No reaction occurs because copper is less reactive than hydrogen, therefore it cannot displace hydrogen from the hydrochloric acid. Therefore no displacement reaction occurs, which means there is no chemical reaction between copper and hydrochloric acid

Magnesium sulfate is an example of a ____

Magnesium sulfate is an example of a salt

general equation for acid and metal

Acid + Metal --> Salt + Hydrogen

what type of salts does hydrochloric acid produce

Hydrochloric acid produces chloride salts

what type of salt does sulfuric acid produce

Sulfuric acid produces sulfate salts

what type of salt does nitric acid produce

nitric acid produces nitrate salts

hydrochloric acid + magnesium --->

hydrochloric acid + magnesium ---? magnesium chloride + hydrogen

hydrochloric acid + _______ ---> magnesium chloride + hydrogen

hydrochloric acid + magnesium --> magnesium chloride + hydrogen

Explain why magnesium reacts more vigorously than zinc or iron, when the three metals react with hydrochloric acid

Because magnesium and hydrogen have the biggest difference in reactivity compared to the difference in reactivity with zinc and hydrogen, or iron and hydrogen. (IRON IS ONLY SLIGHTLY MORE REACTIVE THAN HYDROGEN, MEANING THAT A REACTION BETWEEN IRON AND ACIDS WILL BE A SLOW REACTION) This means that magnesium can easily displace hydrogen from hydrochloric acid (acids)

describe and compare the reactions of magnesium, zinc and iron with acids

magnesium reacts rapidly with acids zinc reacts fairly rapidly with acids iron reacts fairly slowly with acids