The reaction of metals with acids

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The reaction of metals with acids
Revision questions:
 To compare the reactions of different metals with
dilute acids
 To explain the test for hydrogen gas
 To decide which metals react more vigorously from
practical observations
Key words:
Metals, acids, pH, salt, squeaky pop test
Where would you find the
metals from the periodic
table of elements?
Which group are they in?
What are the properties of
metals?
 An acidic substance has a pH of less than 7.
 How do we tell? Use an indicator!
 Acids will react with an alkali (substance with pH above 7) to always form salt and
water!
The most common ones you’ll need to know in your syllabus are:
 Hydrochloric acid (HCl)
 Sulfuric acid (H2SO4)
 Nitric acids (HNO3)
 https://www.youtube.com/watch?v=Na_6j9y9ke8
 When you add an acid to a metal, a colourless and odourless gas is produced. Can
you guess what it is?
Hydrogen gas!
The fizzing or bubbling that you’ve noticed is actually hydrogen gas being
produced from the reaction between the acid and metal and released to the
atmosphere. This shows that a chemical reaction has occurred! Other observations
that you can make is the dissolving of the metal. What do you think is going on in
these experiments?
Acid + metal
salt + hydrogen
e.g. Hydrochloric acid + sodium
sodium chloride + hydrogen
Note: name of the salt is determined by type of metal and name of acid used in the
reaction. Always start with the metal followed by the acid.
If we use hydrochloric acid, the salt will be a chloride
If we use sulfuric acid, the salt will be a sulphate
If we use nitric acid, the salt will be a nitrate
Note: a salt is a substance produced
from the reaction of a metal or
metal compound with acid. The salt
contains the metal and the parts
leftover when the hydrogen is
released from the acid. The salt that
you consume (table salt) is actually
sodium chloride. Please don’t try to
eat other salts as they may be
poisonous!
Let’s look at a few examples:
Magnesium + hydrochloric acid
magnesium chloride + hydrogen
* If we use hydrochloric acid, the salt will be a chloride
Magnesium + sulfuric acid
magnesium sulphate + hydrogen
* If we use sulfuric acid, the salt will be a sulphate
Magnesium + nitric acid
magnesium nitrate + hydrogen
* If we use nitric acid, the salt will be a nitrate
We’re now quite familiar with word equations, but what about symbol equations?
e.g. Hydrochloric acid + sodium
HCl(aq) + Na(s)
sodium chloride + hydrogen
NaCl(aq) + H2(g)
First, you’ll need to know the symbols for the metals (periodic table) and for the
acids. To know the ratios of the metals to the chloride/sulphate/nitrate ions in the
salt, just remember:
For HCl: Group 1 1:1
For HNO3: Group 1 1:1
For H2SO4: Group 1 2:1
Group 2 1:2
Group 2 1:2
Group 2 1:1
Group 3 1:3
Group 3 1:3
Group 3 2:3
We’re now quite familiar with word equations, but what about symbol equations?
e.g. Hydrochloric acid + sodium
HCl(aq) + Na(s)
sodium chloride + hydrogen
NaCl(aq) + H2(g)
Then you’ll need to know which group the metals are in to know the ratios of acids to
metals.
For HCl: Group 1 1:1
For HNO3: Group 1 1:1
For H2SO4: Group 1 1:2
Group 2 2:1
Group 2 2:1
Group 2 1:1
Group 3 3:1
Group 3 3:1
Group 3 3:2
We’re now quite familiar with word equations, but what about symbol equations?
e.g. Hydrochloric acid + sodium
HCl(aq) + Na(s)
sodium chloride + hydrogen
NaCl(aq) + H2(g)
(s), (l), (aq) and (g) are state symbols. Basically:
(s) = solid
(l) = liquid (liquid must be a pure substance
(aq) = aqueous (solution made with water)
(g) = gas
Let’s look at a few examples:
Magnesium + hydrochloric acid
Mg(s) + 2HCl(aq)
Magnesium + sulfuric acid
Mg(s) + H2SO4(aq)
Magnesium + nitric acid
Mg(s) + 2HNO3(aq)
magnesium chloride + hydrogen
MgCl2(aq) + H2(g)
magnesium sulphate + hydrogen
MgSO4(aq) + H2(g)
magnesium nitrate + hydrogen
Mg(NO3)2(aq) + H2(g)
 When you add an acid to a metal, a colourless and odourless gas is produced. Can
you guess what it is?
Hydrogen gas!
The fizzing or bubbling that you’ve noticed is actually hydrogen gas being
produced from the reaction between the acid and metal and released to the
atmosphere. But how do we tell if it really is hydrogen?
 All you need is a lighted splint.
 If it burns and goes out with a ‘pop’ you
know it is hydrogen gas!
What is happening?
Hydrogen + oxygen
water
 You’ve seen that some metals react very vigorously with the dilute acids. You know
this by the large amounts of hydrogen released quickly during the reaction (a lot of
fizzing/bubbling) E.g. magnesium, calcium, potassium
 Some metals do not react as vigorously with the dilute acids (less fizzing/bubbling)
E.g. zinc, iron, lead
 Some don’t react with acids at all! (no reaction/ no fizzing)E.g. copper, gold and
silver
 This is all due to reactivity!
We’ll discuss what this is later on in the topic.
 Metals react with acids to form salt and water
 The named of the salt depends on the type of metal and acid used
 Some metals react violently with dilute acids, while others react less vigorously.
Some do not react at all.
 We learnt how to write word equations
 We learnt a little about writing symbol equations and state symbols
 https://www.youtube.com/watch?v=9hBCLoWwcWo
 https://www.bbc.co.uk/education/guides/zqwmxnb/revision/2
 https://www.youtube.com/watch?v=b1JtmFQzY4Y
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