Formulae and reacting quantities

Question 1

Elements in compounds ending in -ide

Answer 1

contain the two elements indicated by the name

Question 2

Talk about compounds ending in -ate or -ite

Answer 2

contain the elements indicated by the name and oxygen

Question 2

What are the prefixes in chemical formulae?

Answer 2

mono 1
di 2
tri 3
tetra 4
penta 5
hexa 6

Question 3

How to write a basic chemical formula

Answer 3

write down the symbols of both the elements involved

beneath each symbol write the valency

swap the valencies over

if the valencies can be simplified divide them both by the smaller of the two numbers

Question 4

What are group ions?

Answer 4

Group ions contain two or more atoms, and most of them have a negative charge

Question 5

Roman numerals 1-6

Answer 5

I
II
III
IV
V
VI

Question 5

when should brackets be used in a chemical formula

Answer 5

When a formula contains more than one group ion, the group ion must be written in brackets

Question 6

When using Roman numerals to write the chemical formula what must we still do?

Answer 6

cross over the valencies

Question 7

What is the state symbol for a solid?

Answer 7

(s)

Question 8

What is the state symbol for a liquid?

Answer 8

(l)

Question 9

What is the state symbol for a gas?

Answer 9

(g)

Question 10

What is the state symbol for an aqueous solution?

Answer 10

(aq)

Question 11

For most elements, 1 mole is what?

Answer 11

relative atomic mass in grams

Question 12

For the diatomic elements 1 mole is what?

Answer 12

twice the relative atomic mass in grams

Question 13

Formula triangle for solids, liquids and gases…

Answer 13

number of moles = mass in grams/ mass of one mole

n=m/GFM

Question 13

Formula triangle for solutions…

Answer 13

concentration of solution in mol l-1 = number of moles of solute / volume of solution in litres

(c=n/v)

Question 14

What does a chemical formula tell us?

Answer 14

the number of atoms in a molecule of a covalent compound or the ratio of ions in an ionic compound

Question 15

What is percentage composition?

Answer 15

the percentage mass of each element present

Question 16

What formula can be used to calculate percentage by mass

Answer 16

% by mass = m/GFM x 100

m represents the mass of the element that is present in the compound in grams

Question 17

Give an example of a percentage composition question…

Answer 17

Calculate the percentage by mass of oxygen in 1 mole of water (H2O).

GFM of H2O = 18

% by mass of O in H2O= 16/18 x100

Question 18

Two elements which do not contain oxygen will always end in what?

Answer 18

-ide

Question 19

What is the valency of zinc always

Answer 19

2

Question 20

If dealing with prefixes in chemical formulae what must one remember?

Answer 20

do not simplify the valencies

the prefix applies the valency of the element to which it was attached (do not cross the valencies)

Question 21

What is an aqueous solution

Answer 21

compound dissolved in water

Question 22

When balancing chemical equations how do we know if we have a group ion?

Answer 22

The elements will be together (not split up) on either side of the equation