Moles II - TN

Question 1

how many centimetres in a decimetre

Answer 1

10

Question 2

how many cm3 in a dm3

Answer 2

1000

Question 3

equation to find moles using volume

Answer 3

moles = volume(dm3) / 24(dm3)

Question 4

steps to calculate: the volume of O2 needed to react with 10g of N2

Answer 4

• find moles of N2
• mole ratio
• convert moles O2 into volume (moles = volume / 24dm3)

Question 5

what are the three different formulae for moles

Answer 5

• mass(g) / Mr
• volume(dm3) / 24(dm3)
• concentration x volume

Question 6

formula for concentration of a solution

Answer 6

concentration(mol/dm3) = moles of solute / volume(dm3) of solvent

Question 7

what is titration

Answer 7

a practical method used to measure the volume (or ‘titre’) of acid needed to neutralise a particular volume of alkali or vice-versa.

Question 8

what is a volumetric pipette

Answer 8

• measures put 25cm3 very accurately
  (the thing we attached the ball sucker onto)

Question 9

what is a burette

Answer 9

• measures any volume to the nearest 0.05cm3
  (the long glass tube with the tap at the end)

Question 10

how do you calculate the mean titre

Answer 10

using only concordant titres (those within 0.2cm3 of each other)

Question 11

what are the three set up steps for titration

Answer 11

• use a volumetric pipette to place 25cm3 of the unknown alkali into a conical flask
• add a few drops of Phenolphthalein
• fill a burette with known acid and clamp it above the conical flask

Question 12

what are the four steps to find the final titre in titration

Answer 12

• measure initial volume on the burette
• use the burette to add the acid drop by drop while constantly swirling the flask
• close the burette tap as soon as the colour change in the flask becomes permanent
• measure the final volume on the burette

Question 13

what does the mean titre of titration tell you

Answer 13

the amount of acid needed to neutralise the given volume of alkali