moles II

Question 1

equation linking mass, rfm and moles

Answer 1

mass = rfm x moles

Question 2

what is 1000cm cubed in dm cubed

Answer 2

1 dm cubed

Question 3

equation linking concentration, moles, volume

Answer 3

concentration = moles/volume

Question 4

equation linking volume (dm3), moles and 24

Answer 4

volume = moles x 24

Question 5

what is meant by the term concentration

Answer 5

number of particles per unit volume

Question 6

experiment to collect …moles of hydrogen gas

Answer 6

Place 50 cm cubed of hydrochloric acid in a conical flask.
Set up the apparatus shown with the conical flask connected to a 100 cm? gas syringe.
To start the experiment, put the magnesium in the acid and place the bung in the conical flask as soon as possible.
Wait until the reaction has finished, let the syringe cool for a minute, and then read the gas volume.
Repeat the experiment using three different amounts of magnesium.

Question 7

titration experiment

Answer 7

1. In a clean, dry pipette, transfer 25 cm of an alkali into a conical flask.
2. Fill a clean, dry burette with acid.
3. Add a few drops of a suitable indicator to the alkali.
4. Note the starting volume.
5. Add acid into the conical flask and swirl.
6. When the indicator starts to change colour, add the acid dropwise and swirl.
7. When the colour change lasts 10 seconds, stop adding acid, note the new volume.
8. Calculate the titre and repeat until two concordant results are obtained.

Question 8

why is a white tile placed under glass in titration experiment

Answer 8

to allow colour change to be seen

Question 9

why are the same number of indicator drops used each time in titration practical

Answer 9

more accurate results

Question 10

what should you make sure the space below the gap of the burette is filled with solution in titration practical

Answer 10

ensures starting volume is accurate

Question 11

why is the flask swirled as dilute acid is added in titration practical

Answer 11

to mix/distribute solution evenly - so we will see immediate colour change

Question 12

list equipment needed in titration experiment

Answer 12

conical flask
white tile
clamp stand
volumetric bulb flask
volumetric pipette
burette
pipette fillers

Question 13

why is universal indicator not suitable for titration

Answer 13

continuous gradient of colours lack the precision to indicate a precise colour change = use phenolphthalein