Question

Question 3 [20 points 1. Copper sulfide is produced when copper and sulfur are heated together Use the data below, obtained after the heating process, to determine the empirical formula of this compound. Molar masses (e/mol) c S 32.06. 18 points) befor 1 Mass of crucible cover copper (B) 2 Mass of crucible + cover (g) 3 Mass of copper (B) 4 Mass of crucible cover + copper sulfide at constant weight (8)40.23 S Mass of copper sulfide (8) 6 Mass of sulfur in copper sulfide (B) 40.09 39.57 Empirical Formula Empirical Formula WORKINGS Write the balanced chemical equation for the formation of copper sulfide from copper and sulfi A substance was found to contain 45.57 % tin, Sn and 54.43 % chlorine. C. What is the empiri 2. substance? Molar masses (g/mol); Sn 118.71, Cl 35.45. SHOW WORKINGS BELOW [4 points) 3. Complete the following sentences by inserting "empirical" or "molecular. [2 pointsl )A/Anformula indicates the actual numbers and types of atoms in a m .mula indicates the relative numbers of the atoms present molecule Calculate the formula weight of copper() sulfite, Cu,SO.. Atomic weights (amul: Cu e 00 amu] (SHOW WORKINGS). [2 points)

Answer 1

Mass of Copper = [mass of crucible + cover + copper ] - [ mass of crucible + cover]

=(40.09 - 39.57) = 0.52 g.

Mass of Copper sulphide = [ mass of crucible + cover + copper sulfide ] - [mass of crucible + cover) ]

= (40.23 - 39.57) = 0.66 g

Then, mass of sulphur = (0.66 - 0.52) = 0.14

Atomic ratio of Cu and S

Cu : S

=
0.52 5 63.5
:
4 1-2

= 0.00818 : 0.0043

= 1.9 : 1

$\approx$ 2:1

( Atomic mass of Cu is 63.5 and atomic mass of S is 32) .

Hence empirical formula is Cu₂S

Balanced reaction is

Cu + 2S $\rightarrow$ Cu₂S.

2.

Element	% mass	atomic mass	atomic ratio	simple ratio
Sn	45.57	118.71	(45.57/118.71) = 0.383	1
Cl	54.43	35.45	(54.43/35.45 ) = 1.535	4

Hence , empirical formula is SnCl₄

3.

i)

A molecular formula indicates the actual numbers and types of atoms in a molecule.

ii)

An empirical formula indicates the relative numbers of the atoms present in a molecule.