Laboratory Skills Flashcards
What is a Solution
uniform homogenous mixture of two or more substances i.e, solute and solvent
Solution= solute + solvent
What is a Standard Solution?
Standard solution: very precise solution, usually used in quantitative analysis or an analytical procedure
What is a Saturated Solution?
a solution that contains the maximum amount of a particular solute that will dissolve at that temperature.
What is a Supersaturated Solution?
a solution that contains more solute than equilibrium condition allows; it is unstable & the solute may precipitate upon slight agitation or addition of single crystal
Name different ways to prepare solutions of known concerntrations
- Weighing out a solid material of known purity, dissolving it in a suitable solvent and diluting to the required concentration
- Measuring out a liquid of known purity, dissolving it in a suitable solvent and diluting to the required concentration
- Diluting a solution previously prepared in the laboratory
- Diluting a solution from a chemical supplier.
what are the two basic types of balance for weighing chemicals
- Top loading
2. Analytical - more accurate at smaller weigths
Explain the steps for weighing a substance
- Turn on the balance and wait for the display to read zero
- Check the level indicator and do not lean on the bench whilst weighing
- Place a weighing vessel on the balance pan (at this stage on an analytical balance you would close the sliding doors and wait for it to stabilise)
- Press the tare button to re-zero the balance
- Gently add the substance being weighed to the weighing vessel, record the weight and remove the weighed sample.
- NEVER return any unused chemicals to their original container
- Clean spills of the balance with a brush or absorbent lab tissue
Name 4 equipment to measure solutions in
- Beakers / Erlenmeyer flasks
- Burette
- Volumetric flasks
- Gradated Cylinders
Adv/Dis of Beakers
- These measurements have a ±5% error
- Not designed to accurately measure volumes
- Come in various sizes each with different calibration markings
Adv/Dis of Erlenmeyer Flasks
- These measurements have a ±5% error
- Not designed to accurately measure volumes
Adv/Dis of Gradated Measuring Cylinder
- A graduated cylinder marked TC will hold the volume measured but will not deliver that volume to the container when transferred. Some of the liquid will remain behind in the graduated cylinder. If an exact amount is to be transferred, the graduated cylinder should be marked. TD
- Tolerances vary with the size of the graduated cylinder. This tolerance is generally marked on the cylinder
- Water and aqueous solutions will form a concave meniscus as the water molecules are more strongly attracted to the glass than each other. The bottom of the curved surface is read at eye level.
Volumetric Flasks
- Calibrated to contain a precise volume- often used for solutions in quantitative analysis
- The neck of the flask has a single calibration mark- line the bottom of the meniscus up with this mark
- The volume is given on each flask and tolerances are usually within a few hundredths of a ml
Micropipettes
smaller devices used to measure out solutions accurately
Lab Safety
- Read and understand the whole of the introduction and experimental section before starting the practical.
- The notes for each unit contain specific safety instructions.
- Never eat, drink smoke, apply make up or chew gum in the laboratory
- Immediately Report ANY accidents to the nearest demonstrator or staff member.
- Always wear white coats, gloves and safety spectacles in the laboratory.
- Do not wear them in public areas such as the library and canteen.
- NO LAB COAT, NO PRACTICAL, NO MARK, NO EXCEPTIONS
Waste Disposal
- Sharps must go into sharps bins
- Pipette tips are treated as sharps
- Gloves and bulky non-sharp waste go into orange bags
