module 3 revision

Question 1

types of chemical reactions

Answer 1

-synthesis
-decomposition
-precipitation
-combustion reactions

Question 2

synthesis reactions

Answer 2

when two different substances combine and form ONE substance together

A + B => AB

Can be ionic or covalent.

Ionic example: magnesium and sulfur
Mg(s) + S(s) => MgS(s)

Covalent example: carbon and oxygen
C(s) + O2(g) => CO2(g)

Question 3

decomposition reactions

Answer 3

opposite of synthesis reactions, a substance splits into two substances (decomposes)
AB => A + B
HEATING UP A CARBONATE WILL RESULT IN DECOMPOSITION

Lets look heat:
Ionic solid: MgCO3(s) => CO2(g) + MgO(s)
Lets look at light (not common)
AgCl(s) => Ag(s) + 1/2Cl(g) - silver halides
Electricity
2H2O(l) => 2H2(g) + O2(g)

Question 4

precipitate reactions - the “partner” up reaction equations or cross react

Answer 4

The definition of a precipitation reaction is when two (or more) soluble salts react to form an insoluble product
Lets look at sodium chloride and silver nitrate:

NaCl(aq)+ AgNO3(aq) => NaNO3(aq) + AgCl(s) - look at the solubility table rules, all chlorides are soluble except silver chloride
Solid must come out

Question 5

Combustion reactions (common and mathematical)

Answer 5

“ignition for a fuel”
Requirements for a combustion reaction:

-fuel
-oxidants
-heat

Two things that come out are water (in gas form) and carbon dioxide comes out as a product (as a complete reaction)

Question 6

example of combustion reactions (complete combustion - finishes off with Co2)

Answer 6

Octane (common fuel to fill the car) - burns well with oxygens
C8H18(l) + O2(g) => H2O(g) + CO2(g) (complete reaction)
Now to balance:
C8H18(l) + 25/2O2(g) => 9H2O(g) + 8CO2(g)

Question 7

example of combustion reactions (incomplete)