7/28/2019 Mg + HCl

1/17

Reactions between acids and metals

The aim of this lesson is for you to understand

how acids react with metals, what is producedwhen they react and how to test for it.

You will see one demonstration and do one

experiment!

7/28/2019 Mg + HCl

2/17

Magnesium is a metal:

7/28/2019 Mg + HCl

3/17

Magnesium is a metal:

It is an element so only contains one

type of atom (magnesium atoms!)It is shiny

It conducts heat

It conducts electricity

7/28/2019 Mg + HCl

4/17

Hydrochloric acid is a compound

It contains hydrogen atoms andchlorine atoms in pairs

Each pair of atoms is called a

molecule

There are thousands of the

molecules in a bottle, all floating

around in water

7/28/2019 Mg + HCl

5/17

Each hydrochloric acid molecule is

made up of one hydrogen atom and

one chlorine atom

Hydrogen

atom

Chlorine

atom

Hydrochloric

acid molecule,

formula HCl

7/28/2019 Mg + HCl

6/17

What happens when we put

magnesium into hydrochloric acid???

7/28/2019 Mg + HCl

7/17

What is your prediction?

7/28/2019 Mg + HCl

8/17

Looking at what happened in the test tube:

The magnesium reacted with thehydrochloric acid

The reaction happens when acid

molecules touch the magnesium

When the reaction happened a gas is

given off

7/28/2019 Mg + HCl

9/17

Zooming into a microscopic level..

We are going to look at thesurface of the magnesium

7/28/2019 Mg + HCl

10/17

We are now inside the test tube!

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

H

Cl

Magnesium strip

H

Cl

H

Cl

H

Cl

H

Cl

H

Cl

H

Cl H

Cl

H

Cl

H

Cl

H

Cl

H

ClAcid molecules

in the water

Acid molecules

in the water

Acid molecules

in the water

Acid molecules

in the water

7/28/2019 Mg + HCl

11/17

We are now inside the test tube!

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

H

Cl

H

Cl

The acid particles have to touch the

magnesium to react with it

7/28/2019 Mg + HCl

12/17

We are now inside the test tube!

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

H

Cl

H

Cl

The acid particles have to touch the

magnesium to react with it

7/28/2019 Mg + HCl

13/17

We are now inside the test tube!

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

H

Cl

H

Cl

Two acid molecules react with onemagnesium atomWhen they react the atomsre-arrange themselves into

new molecules

7/28/2019 Mg + HCl

14/17

We are now inside the test tube!

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg

Mg

Cl

H H

Cl

The atoms now make 2 newmolecules

Magnesium

chloride which

stays in the

water

Hydrogen which is a

gas so bubbles up tothe surface

The magnesium

disappears

7/28/2019 Mg + HCl

15/17

So, how can we tell if the bubbles were really

hydrogen molecules????

Hydrogen is explosive, so

it will make a lighted splint

go pop. This is the test

for hydrogen!

pop!

7/28/2019 Mg + HCl

16/17

Describing the reaction

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg Mg

MgMg Mg Mg Mg MgMg Mg Mg Mg Mg Mg Mg

H

Cl

H

Cl

MgH

Cl

H

Cl

Mg HCl

HCl

+ +

magnesium + hydrochloric acid magnesium chloride + hydrogen

Mg + 2HCl

MgCl2 + H2

7/28/2019 Mg + HCl

17/17

More equations to fill in the gaps!

zinc + hydrochloric acid ______________ + ____________

________ + hydrochloric acid lithium chloride + hydrogen

_______ + sulphuric acid calcium sulphate + ____________

zinc chloride hydrogen

hydrogen

lithium

calcium

Homework: design a sheet to tell someone how to makehydrogen and how to test for it.