Quantitative Chemistry (Part 2) - Unit 1 Topic 7

Question 1

What is empirical formula?

Answer 1

Simplest whole number ratio of atoms of each element presented in a compound.

Question 2

What is molecular formula?

Answer 2

Shows actual number of atoms of each element in a molecule

Question 3

What does hydrated mean?

Answer 3

Crystalline and containing water molecules

Question 4

What does anhydrous mean?

Answer 4

A substance containing no water molecules

Question 5

What is water of crystallisation?

Answer 5

Water molecules that form an essential part of the crystalline structure of a compound

Question 6

Calculate the empirical formula of the compound:

6g of silicon oxide are formed from 2.8g of silicon

Answer 6

Si = 2.8g
O = 3.2g

2. 8/28 = 0.1 mol
3. 2/16 = 0.2 mol

Si = 0.1/0.1 = 1 
O = 0.2/0.1 = 2

SiO2

Question 7

How is water of crystallisation removed?

Answer 7

Heating to a constant mass

Question 8

Calculate the percentage of water;

CuCl2.2H2O

Answer 8

21%

Question 9

What is the test for oxygen?

Answer 9

Relights a glowing splint

Question 10

What does hearing to a constant mass mean?

Answer 10

Repeatedly heating, cooling and weighting until 2 records of mass are the same