Chemical Calculations: Revision
Francine Taylor-Campbell, Contributor

Attempt these questions without using textbooks or notes at first, the complete, if necessary, by referring to texts or notes.

COMPLETE THIS TABLE

FORMULA	MASS OF 1 MOLE	# MOLES	GIVEN MASS/g	VOLUME AT RTP/dm3	# FORMULA UNITS (L)
CO2	44	0.2	8.8g	4.8	0.2L
H2S			17g
H2					1.5L
O2				6
N2		3
CaCO3			40g
Al(NO3)3		0.2
An alkane			116	48dm3

2. Multiple-choice questions on the mole
Choose from A 2, B 4, C 6, D 8.

1. The number of moles of molecules in 16g H₂
2. The number of moles of atoms in 28g N₂
3. The number of moles of a gas in 89.6dm³ at RTP
4. The volume in dm³ of 8g O₂ at RTP
5. The number of moles of atoms in 88g CO₂
6. The mass of 0.25 moles of Mg
7. The mass of 0.04 moles of CaCO₃
8. The number of moles of S containing 1.2*10²⁴ atoms
9. The mass of moles of H₂
10. The mass of 3 dm³ O₂ at RTP

3. PERCENTAGE COMPOSITION AND FORMULAE

Calculate the percentage of (a) Fe in Fe₂(SO₄)₃ (b) H₂O in Na₂CO₃.10H₂O (c) Calculate the molecular formula of a substance which contains 80% C and 20% H.

4. CALCULATIONS ON EQUATIONS. USE THE EQUATION

2KC1O₃(S) = 2KCl(s) + 3O₂(g) to find:

a. The number of moles of oxygen which can be obtained from three moles of potassium chlorate
b. The number of moles of KC1O₃ which would give two moles of O₂.
c. The volume of O₂ (at RTP) obtainable from 12.25g KC10₃.
d. The mass of KC1 obtainable from 12.25g KC1O₃.
e. The mass of KC1O₃ needed to obtain 14.9g KC1.
f. The loss in mass when 245g KC1O₃ is heated.

5. VOLUMETRIC ANALYSIS. COMPLETE THIS TABLE

FORMULA	MASS OF 1 MOLE	VOLUME OF SOLN./cm3	# OF GRAMS IN VOL	CONCENTRATION g/dm3	CONCTRATION Mol/dm3
NaOH		1000	6.00g	4.8
HNO3		400	2.40g
H2SO4		300		5.20
Na2CO3		250		6	0.045
NaHCO3		5 dm3			1.500
H2X			4.50g	9.00	0.100

Francine Taylor-Campbell is an independent contributor. Send questions and comments to kerry-ann.hepburn@gleanerjm.com