Chem Practical Flashcards
Titration table?
Titration number
Initial burette reading /cm3
Final burette raring /cm3
Volume of (titrant) /cm3
Check out
Redox Rxctns w/ KMnO4 / KI / H202
** If H2O2 is added
- Test for OXYGEN w/ glowing splint
- KMnO4. It is OA
- Test for RA
- Purpler to colurless ++++
- KMnO4 is reduced. RA is oxidised - KI. It is RA
- Test for OA
Colourless to brown +++
- KI is oxidised. OA is reduced
Effect of washing titration conical flask with water, titrant & analyte.
- Washing with distilled water ONLY:
- GOOD. No effective on results
- Does not change number of reactant moles in the conical flask
- Titration measures the endpoint based on moles, not based on dilution - Washing with titrant (solution from the burette)
- BAD. Adds more moles of titrant than expected
- Leads to lower than expected volume reading of titrant used - Washing with analyte (solution in conical flask)
- BAD. Increases number of moles of reactant in conical flask
- Titration reading higher than expected
How to wash burette, pipers & conical flask
- Burette:
Rinse w/ distilled water then titrant
Pipette
Rinse with water then analyte (solution for conical flask)
Conical flask
Rinse with water ONLY
Reminder: Always link what Qn asked to titration results (Eg: More or less of solution XX)
4/5 Common Sources of Error & Solutions (Them & Bio)
- Thermometer reading is not accurate
- Use a thermometer with a higher precision - Temperature of solution may changed over time
- Use a thermostatically-controlled water bath OR Use a insulated beaker - Measuring cylinder is not accurate
- Use burette or pipette - Hard to tell colour change of solution
- Compare against a colour chart - (BIO) Cannot start/end experiment at the same time for all variables
Eg: Can’t remove all potatoes from salt solution at exactly 5 min at the same time
- Carry out experiments separately
When to draw line graph touching origin?
When you are certain that a 0 value for IV will give you a 0 value for the DV
Heating/ thermal decomposition table
Mass of empty test tube /g
Initial mass of beaker/container with XX /g
Final mass of beaker/container with XX after heating /g
Loss/gain in mass /g
5 Observations for Heating Solids
Write down:
- initial colour of solid
- Gases produced
- final colour of solid
- Whether solid melts/change colour
- Whether condensation droplets form on sides of boiling tube
5 Displacement Rxctns Observations
Write down:
- Initial Colour of solution?
- Final colour of solution?
- Formation of coloured ppt ?
- Test tube feels HOT/COLD?
- Any solid deposited onto more reactive metal ? (Metal displacement)
WRITE DOWN EVERYTHING
Purpose of Cotton Wool in Acid carbonate rxctns
Allows CO2 gas to escape & prevents acid from splashing out of flask
What are catalysts?
Catalyst are a substance that speeds up the ROR by finding an alternative pathway with lower activation energy. They remain chemically unchanged afterwards.
They are specific in action, sensitive to temp, pH and and made of proteins
5 Rate of rxctn factors & Exp
- Concentration (aqueous stuff only) OR Number of Moles of any substance (limiting or not)
- Conc increase, ROR increase
- More reactant particles per unit volume
-Freq of effective collision increase
- ROR increase - Catalyst
- Increase ROR
- Find alt pathway with lower act energy
- More reactant particles ___ possess energy equal to or greater than act energy
- Freq of effective collision between ___ increase
- ROR increase - Temperature
- Temp increase ROR increase
- Reactant particles ___ gain heat and kinetic energy so they move faster
- More reactant particles ___ possess energy equal to or greater than act energy
- Freq of effective collision increase
- ROR increase - Particle size (Solids)
- Particle decrease, ROR increase
- Lower PS increases SA to Vol ratio of solid reactant ___ in contact with reactant ___
- Freq of effective collision increase
- ROR increase - Pressure (gases)
- Higher pressure
- Reactant Particles ____ closer packed
- More reactant particles per unit volume
- Freq of effective collision between ____ increase
- ROR increase
NH3
Pungent, colourless gas turns damp red litmus paper blue
O2
Colourless, odourless gas delights glowing splint
