Remove content quiz for EOY Exam

In the chemical equation 2H₂O₂(aq) → 2H₂O(l) + O₂(g),

H₂O and O₂ are.........

• the reactants

• the yield

• the products

• state symbols

Answer explanation

The reactant is H₂O₂

Reactants react & products are made

State symbols show the physical state of the reactants & products

(s) = solid

(l) = liquid

(g) = gas

(aq) = dissolved in water

Chemical reactions

• create and destoy atoms

• only occurs outside living organisms

• occurs only in living organisms

• produce new substances

The products of a reaction have the same ________as the reactants.

(a)  

• molecules

• mass
• formulas

• coefficients

Answer explanation

This is the law of conservation of mass

Total mass does not change in a chemical reaction - this can be confusing because in some reactions you measure loss of mass - this is because a gas is made and gases still have mass.

Another way of explaining it is that the atoms in the products are the same as the atoms in the reactants - atoms cant be created or destroyed - they are just rearranged to form different substances.

What is a coefficient?

• The small number on the right of the chemical symbol.
• The large number to the left of a formula.
• the total number of atoms in a compound

Answer explanation

It can also be known as the balancing number

To balance a chemical equation, it may be necessary to adjust the

• formulas of the products

• subscripts

• coefficients

• number of products

This is the chemical formula for aluminium oxide:
Al₂O₃

What does the small ₃ after the O tell you?

• its the coefficient for oxygen

• how many oxygen atoms there are in aluminium oxide

• the number of aluminium oxide molecules

When balancing this equation, .....Fe + .....Cl₂ → 2FeCl₃

what are the correct coefficient for Fe and Cl₂?

• 1 & 3

• 3 & 2

• 2 & 3

• 2 & 6

Answer explanation

There are 6 chlorine atoms in 2 FeCl₃

so there must be 6 chlorines on the left.

Each chlorine molecule (Cl₂) has 2 atoms

so there must be 3 Cl₂ to make 6

How many atoms of aluminum are on each side of the following equation: 4Al + 3O₂ --> 2Al₂ O₃

• 2
• 6
• 1
• 4

Balance this equation, .....CaCO₃(s) → .....CaO(s) + .....CO₂(g)?

• 3,1,2

• 1,1,1

• 1,3,1

• 2,6,3

Answer explanation

both sides have the same number of calcium, carbon and oxygen atoms so it is already balanced.

you don't actually need to write the 1s in front as no number means 1.

Balance this equation.
..... Mg + . .... Cl₂ --> ..... MgCl₂

• 1, 2, 1

• already balanced
• 2, 1, 1

• 1, 1, 2