5.1 MOLES II
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How to convert cm to dm
Divide by 1000
How to convert dm to cm
x 1000
Moles equation (volume)
Moles = Volume (dm) / 24dm
Volume equation for moles
Volume = moles x 24dm
How do you calculate gas moles
• Convert volume to moles • Balance moles from equation • Convert moles to volume
What is volume measured in
cm or dm
What is concentration measured in
mol/dm
Concentration equation for moles
Concentration = Moles / Volume
Moles equation (concentration)
Moles = concentration x volume
What must you do FIRST in every moles calculation
Convert cm to dm
What is used to measure 25cm of acid/alkali in a titration
Volumetric pipette
What is used to dispense acid/alkali into the other
Burette
What does a burette measure to
The nearest 0.05cm
How to setup a titration (for finding concentration of alkali)
• Use the volumetric pipette to place 25cm of unknown alkali into a conical flask • Add indicator • Fill a burette with a known acid and clamp it above the conical flask
How to perform a titration (for finding concentration of alkali)
• Measure the intital volume of the known acid on the burette to the nearest 0.05cm • Use the burette to add the acid into the conical flask, drop y drop swirinling the flask • Close the burette tap as soon as the colour in the conical flask changes • Measre the final colume of the known acid on the burette to the nearest 0.05cm
How to get results from a titration
• Calculate the titre (final volume - initial volume) • Repeat to get concordant (within 0.2cm) titres
How do you calculate the mean titre
Use the concordant titres and calculate the mean
How to work out the unkown concentration from a titration
• Convert volume to moles of known substance • Use mole ratio from equation to find moles of unkown substance • Convert moles to concentration of unknown substance