(GReen) Moles III (solutions)

Question 1

What is the equation for concentration

Answer 1

Conc = moles / volume

Question 2

What is the equation for g dm^-3

Answer 2

Conc x rmm

Question 3

What is the definition of standard solution

Answer 3

Is a solution which is made to an accurately know concentration . A standard solution is prepared by taking a know mass of solute and making this up to a known volume of solution in a volumetric flask

Question 4

Lay out the procedures for making a standard solution

Answer 4

1. Accurately weigh solute
2. Dissolve solute in a small amount of solvent , warming if necessary
3. Transfer to a volumetric flask
4. Rinse all solution into flask with more solvent
5. Carefully make up to the mark on the flask
6. Invert 5 times

Question 5

How do you find new concentration of a solution

Answer 5

New concentration = dilution factor x old concentration

Question 6

What is the equation for dilution factor

Answer 6

Dilution factor = old volume / new volume

Question 7

Give the equation for percentage error

Answer 7

%error = error on equipment x times used / measureMENT taken

Question 8

describe operator error = ‘blunders’

Answer 8

These are due to carelessness or misuse of apparatus; careful work is needed at all times.
Errors due to misreading apparatus can be avoided if figures are written down in a systematic fashion as they are taken, and then checked. Such errors cannot be quantified.

Question 9

describe Instrument calibration errors

Answer 9

Different readings may be obtained using different items of the same equipment. This is particularly true of thermometers - if absolute values of temperature are required rather than differences it may be necessary to check the readings of thermometers against each other.
Cheap thermometers may vary by 0.5oC – 1oC. However, the error when temperature
differences are measured may reasonably be ignored.

Question 10

describe Precision errors

Answer 10

Precision errors are the only types that show a reasonable degree of experimental
reproducibility. Such errors may therefore be quantified.
Individual pieces of equipment are built to specified standards. The higher the degree of precision, the greater the cost of the apparatus.

Question 11

what is the uncertanty in Balances.

Answer 11

+/- 0.005g per reading.

Question 12

what is the uncertanty in Measuring Cylinders

Answer 12

+/- 1 cm3.

Question 13

what is the uncertanty in Pipettes

Answer 13

0.1cm3

Question 14

what is the uncertanty in Burettes

Answer 14

+/- 0.05 cm3