Practical questions Flashcards
How does increasing the mass of CaCO3 added affect the gas volume?
CP1- Measure the molar volume of gas
. If in excess, no effect
- if liimiting reagent> will increase
Possible errors? How to pattern?
CP1- Measure the molar volume of gas
Some gas can escape before bung is replaced to conical flask : seal apparatus using gas syringe or bung
- Bung not airtight
- Some CaCO3 lost whilst transferring from weigh boat to conical flask
- CO2 is slightly soluble in water > exact volume not measured
Why do you need to be quick when transferring the CaCO3 to the boiling tube + replacing the bung?
Why is a mass of above 0.04g not used?
CP1- Measure the molar volume of gas
To minimise gas loss
.Use of over 0.40 g of calcium carbonate will result in the volume of gas produced exceeding the capacity of the measuring cylinder.
-If larger masses of calcium carbonate are to be used then a larger measuring cylinder will be required.
How do you prevent gas escaping?
CP1- Measure the molar volume of gas
Place the solid reactant upright inside a sample tube in the conical flask, tipping the tube over by moving the conical flask around to start the reaction
CP2- use a standard solution to find the concentration of a solution of
Why is there no need to dry the conical flask after washing it out between trails?
sodium hydroxide.
the water will not change the number of moles of NaOH as this is measured before it is put into the flask
Why should the pipette be rinsed with sodium hydroxide solution after washing it with water?
water left in the pipette will dilute the sodium hydroxide, changing the number of moles used
