Chemical Equations | Environmental Chemistry | Chemistry | FuseSchool

chemical equations can sometimes look a

bit daunting especially when there are

lots of different compounds and state

symbols involved but fear not help in

this lesson about chemical equations

quite simply a chemical equation shows

the overall chemical change of reactants

into products it's a bit like a detailed

cooking recipe but where all the

ingredients and all the products are

written down even the ones you can't

necessarily see the reactants are what

you start with and the products are what

are formed there are two ways of writing

chemical equations word equations and

symbol equations when they are written

both types show the reactants on the

left of an arrow and the products on the

right the arrow is there to show that

the reaction is irreversible if you like

it shows the direction of the reaction

and that is one way a bit like a one-way

street you can traverse along a one-way

street and you can traverse an

irreversible reaction let's look at a

word equation this is a way of

summarizing a chemical reaction for

example the neutralization of

hydrochloric acid with sodium hydroxide

we would write sodium hydroxide plus

hydrochloric acid then the arrow sodium

chloride plus autumn the plus sign

indicates that there is more than one

reactant or product on each side of the

equation and you'll note that reactants

are on the left and the products are on

the right we've also written this all on

a single line it makes it a lot easier

to read this way so when you write your

equations try to keep all of the

information on a single line if you

can't then the area becomes an important

separator the rule of reactants on the


and projects on the right still applies

because if not the equation to become a

jumbled mess clearly written equation is

always easier to understand a word

equation provides a good summary but a

simple equation provides more

information it shows more detail and

that allows us to see how many atoms and

molecules are involved in each reaction

so if we look at the neutralization

equation again the symbol equation is

written NaOH plus HCl as the reactants

then an arrow to indicate the

irreversible reaction which gives NaCl

plus h2o as the products the little

matters in brackets are state symbols

they show the state of matter of each

product and reactant and this is covered

in more detail in our lesson state

symbols and chemical equations there are

occasions where a reaction is reversible

due to the changes in surroundings for

example pressure concentration pH and

temperature and where this is the case

we draw a double arrow made of two half

arrows pointing in opposite directions

and this indicates that the reaction can

go either way

the formation of ammonia from nitrogen

and hydrogen is an example of a

reversible reaction

the key thing here is that you recognize

the reversible reaction by the double

arrows and you'll notice some numbers in

front of the hydrogen and ammonia

formulae and these are there to make the

equations balanced you can find out more

about this in our balancing equations

lesson and so to summarize a chemical

equation shows the overall chemical

change of reactants into products we

usually write reactants on the left of

the arrow and products on the right a

single arrow means that the reaction is


and two oppositely pointing half arrows

means the reaction is reversible and

that completes our overview of chemical