AS TRANSITION COURSE,MEASURING AMOUNT OF SUBSTANCE

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AS TRANSITION COURSE
SUMMER 2012
PART 1: MEASURING AMOUNT OF
SUBSTANCE
MASS VOLUME MOLAR MASS AVOGADRO
CONCENTRATION ATOM ION MOLECULE

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COURSE OUTLINE
OCR Chemistry A
Unit 1 ­ Autumn Term 2012
Atoms and Electron Structure
Moles, Equations and Acids
Structure and Bonding
Redox, Group 2 and Group 7
Unit 1 Exam ­ January 2013 ­ 1 hour ­ 90 UMS ­ 30% of total
Unit 2 ­ Spring Term 2013
Basic Concepts in Organic Chemistry
Alkanes and Alkenes
Haloalkanes and Alcohols
Enthalpy Changes
Rates and Equilibrium
Modern Analytical Techniques
Chemistry of the Air
Sustainability
Unit 2 Exam ­ May 2013 ­ 1 hr 45 mins…read more

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MEASUREMENTS IN CHEMISTRY
Mass
Convert the following into grams:
a) 0.…read more

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What is a mole?
Atoms and molecules are very small ­ far too small to count individually!
It is important to know how much of something we have, but we count particles in MOLES
because you get simpler numbers
1 mole = 6.02 x 1023 particles
(6.02 x 1023 is known as Avogadro's number)
a) If you have 2.5 x 1021 atoms of magnesium, how many moles do you have?
b) If you have 0.…read more

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How can you work out how many moles you have?
a) From a measurement of MASS:
You can find the number of moles of a substance if you are given its mass and you know its
molar mass:
number of moles = mass/molar mass
n = m/mr
Mass MUST be measured in grams!
Molar mass has units of gmol-1
1. Calculate the number of 2. Calculate the mass of: 3. Calculate the molar mass of
moles present in: the following substances:
a) 2.…read more

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From a measurement of AQUEOUS VOLUME:
You can find the number of moles of a substance dissolved in water (aqueous) if you are
given the volume of solution and you know its molar concentration:
number of moles = aqueous volume x molar concentration
n = V x C
Aqueous volume MUST be measured in dm3!
concentration has units of moldm-3
If you know the molar mass of the substance, you can convert the molar concentration into a
mass concentration:
Molar concentration (moldm-3) x mr =…read more

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From a measurement of GASEOUS VOLUME:
You can find the number of moles of a gas if you are given the volume of the gas:
number of moles = volume / 24
n = V / 24
24 dm3 is the volume occupied by 1 mole of any gas at room temperature and
pressure
Volume MUST be measured in dm3!
1. Calculate the number of 2. Calculate the volume of gas 3.…read more

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