Download Module 1 - Hartismere

AS Chemistry Revision
Module 1
( Module F331 – “ Chemistry of Life ” )
Practice Questions
and worked answers on
particular skills
Name: _______________________
1] Ar, Mr, Moles and Avogadro
Ar
= Atomic mass (also known as Relative Atomic Mass/ RAM )
Remember: this is the mass of an atom of a particular element compared with / relative to
the mass of an atom of carbon-12. This number is different for each element
and you get it straight from the periodic table box (it’s the bigger of the 2
numbers). No units of measurement.
Mr
= Molecular mass (aka .. “Relative Molecular Mass/ RMM / Relative Formula Mass)
Remember: this is the sum of the Ar’s of all the elements in a compound.
No units of measurement.
Mole =
amount of a substance with 6.02 x 10
23
(Avogadro’s number) particles in it.
23
eg/ 1 mole of fluffy pillows = 6.02 x 10 fluffy pillows.
The mass of 1 mole of a substance is the same as its Mr (in grams).
u Calculating number of moles of substance in a give mass
You can just use the equation above without any rearrangement. This type of
question is only worth 1 mark on module 1 exams, and is nearly always part of a larger
question.
Questions to try - on calculating number of moles of substance in given mass:
1] How many moles in each of the following:
a)
b)
c)
d)
e)
4.5g of water (H2O) ?
0.9g of glucose (C6H12O6) ?
3.2g of copper sulphate (CuSO4) ?
0.135g of water ?
25g of Calcium carbonate (CaCO3) ?
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u Calculating mass when you know the number of moles:
Re-arrange the equation to give you the unknown on its own:
Questions to try - on calculating mass given the number of moles:
2] What is the mass of :
a) 0.1moles of sulphuric acid (H2SO4) ?
b) 0.3moles of copper nitrate ( Cu(NO3)2 ) ?
c) 1.5 moles of ethanoic acid ( CH3COOH ) ?
d) 0.01moles of glucose ( C6H12O6 ) ?
u Balancing & Writing Equations:
Questions to try - on balancing equations:
3] Balance the following:
a)
b)
c)
d)
e)
Al + Cr2O3 g Al2O3 + Cr
Fe2O3 + CO g Fe + CO2
Mg + N2 g Mg3N2
Fe + H2O g Fe3O4 + H2
C6H14 + O2 g CO2 + H2O
4] Write balanced symbol equations for the following:
a) Hydrogen + Copper oxide g Copper + Water
b) Propane + Oxygen g Carbon dioxide + Water
c) Magnesium + Sulphuric acid g Magnesium sulphate + Hydrogen
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u Reacting Masses:
You can predict how much of a substance will be made by a chemical reaction with very
little information. As long as you know the mass of one of the reactants and the balanced
equation, you’re away……….
Worked example:
CaCO3 + 2HCl g CaCl2 + H2O + CO2
Calculate the mass of carbon dioxide that would be formed if 2.5g of
calcium carbonate reacted completely with hydrochloric acid ?
Questions to try - on reacting masses:
5]
CH4 + 2O2 g CO2 + 2H2O
a) From the equation, how many moles of CO2 are produced when 1 mole of methane is
combusted ?
b) What is the mass of 1 mole of methane ?
c) How many moles of methane are there in 1.0g of methane ?
d) What mass of carbon dioxide would be produced if 1.0g of methane were burnt ?
e) What mass of water would be formed if 2.0g of methane were combusted ?
f) What mass of methane would have to be burnt to produce 10.0g of carbon dioxide?
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6] Sodium hydroxide neutralises hydrochloric acid :
NaOH (aq) + HCl (aq) g NaCl (aq) + H2O (aq)
a) It takes 4g of NaOH to neutralise all the HCl. How many moles of NaOH are there in 4g of it ?
b) How many moles of NaOH does it take to neutralise 1 mole of HCl ? (from the equation)
c) What mass of HCl was neutralised by 4g of NaOH ?
7] Chlorine reacts with Sodium Bromide, displacing it.
Cl2 (aq) + 2NaBr (aq) g 2NaCl (aq) + Br2 (aq)
What mass of Br2 is formed when 14.2g of Cl2 reacts ?
8] Nitroglycerine is used as an explosive. The very quick production of gases in a confined space
is the cause of an explosion. This equation shows how it reacts :
4C3H5(NO3)3 (l) g 12CO2 (g) + 10H2O (l) + 6N2 (g) + O2 (g)
a) What mass of Nitrogen would be produced if 100g of nitroglycerine breaksdown ?
b) What mass of Water would be produced if 50g of nitroglycerine broke down ?
9] Aspirin, C9H8O4 , is made by the reaction:
Salicylic acid + Ethanoic anhydride g Aspirin + Ethanoic acid
C7H6O3
+
C4H6O3 g
C9H8O4
+
C2H4O2
How many grams of salicylic acid are needed to make one aspirin tablet, which
contains 0.33g of aspirin ?
10] Nitrogen Monoxide (NO) is a pollutant gas which comes out of vehicle exhausts.
One technique for reducing the quantity of nitrogen monoxide in exhaust fumes is to
inject a stream of ammonia (NH3). This converts NO to harmless products – nitrogen
and water.
4NH3
(g)
+ 6NO (g) g 5N2
(g)
+ 6H2O (l)
An average vehicle emits 5g of nitrogen monoxide per mile. Assuming a mileage of
10,000 miles per year, what mass of ammonia would be needed to clean up the exhaust
fumes (in kilograms per year) ?
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u Different types of formulae:
There are a number of different ways of showing the formula of a compound.
Questions to try - on formulae:
11] Give the structural and skeletal formulae of the following:
a) Propane (C3H8) ?
b) Pentanol (C5H11OH) ?
c) But-2-ene (C4H8) ?
d) CH3(CH2)3CH2OCH2CH3 ? What homologous series is this part of ?
e) CH3 CH2 CH2 CH2 CHOHCH2CH3 ? Name this.
f) CH3 CH(CH3) CH2 CH2 CH3 ?
g) Heptan-2,2,3-triol ?
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u Working out the EMPIRICAL formula of a compound from experimental results:
You can work out the empirical formula of a compound if you know the relative
amounts of each element in it. These element figures are usually found out by experiment
– where the compound is blasted apart !
Worked example:
What is the empirical formula of a compound, given that it contains
77.7% Fe and 22.3% O ?
Questions to try - on empirical formula:
12] Calculate the empirical formula of the following:
a) A compound contains: C (54.5%), H (9.10%) and O (36.4%) ?
b) A compound contains: Ni (37.9%), S (20.7%) and O (41.4%) ?
c) A compound contains: C (18.24%), H (0.76%) and Cl (81.00%) ?
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u Isotopes & their Average Mass
Isotope = Same number of protons, different number of neutrons.
Questions to try - on isotopes:
13]
a) Calculate the average atomic mass of the following elements:
(i) Gallium has common isotopes: Ga-69 (60.2%) and Ga-71 (39.8%).
(ii) Magnesium has 3 common isotopes : Mg-24 (78.6%), Mg-25 (10.1%) and Mg-26 (11.3%).
b)
Use the information displayed in the chart to
calculate the average atomic mass of Germanium ?
c)
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u Radioactive Decay
3 types of decay : alpha, beta and gamma.
Questions to try - on radioactive decay:
14] Copy and complete the following:
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u Light Reactions
There are 2 equations that you need to know:
[For all Qs: speed of light = 3x108 m/s and Planck’s constant = 6.63x10-34 j/Hz ]
Questions to try - on light:
15]
a) What is the wavelength of light with a frequency of 500 Hz ?
b) What is the wavelength of light which has an energy of 210 joules ?
c) Xrays have a frequency of 7.02x1015 Hz. What is the energy of a photon of this
radiation ?
u Bond enthalpy calculations:
You will need this data to help you (all are measured in Kj/mol) :
[ It’s always worth drawing out the structural formula of the compounds to help you
determine the number of each type of bond !]
Questions to try - on bond enthalpy:
16] Calculate the enthalpy change for each of the following reactions using bond
enthalpy data (note: O=O is 798 kj/mol and Br-Br is 183 kj/mol)
a) C2H4 + HBr g C2H5Br
b) CH2=CH-CH3 + Br2 g CH2BrCHBrCH3
c) C6H13OH + 9.5O2 g
6CO2 + 7H2O
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Answers to MODULE 1 practice Qs – skills
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