Experimental Techniques (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards
Exam code: 0654 & 0973
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Which piece of apparatus is used to measure a variable volume of liquid up to 50 cm3 with the greatest accuracy?
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Which piece of apparatus is used to measure a variable volume of liquid up to 50 cm3 with the greatest accuracy?
A burette is used to measure a variable volume of liquid with the greatest accuracy. Note: the scale reads from 0 cm3 at the top to 50 cm3 at the bottom.
A gas syringe is used to measure the volume of a ______, whereas a volumetric pipette is used to measure a fixed volume of a ______.
A gas syringe is used to measure the volume of a gas, whereas a volumetric pipette is used to measure a fixed volume of a liquid.
True or False?
A measuring cylinder is the most accurate apparatus for measuring an exact fixed volume of liquid such as 25 cm3.
False.
A volumetric pipette is the most accurate apparatus for measuring an exact fixed volume. A measuring cylinder is used only when approximate volumes are acceptable.
How should you position your eye when reading the scale on a measuring cylinder to avoid a parallax error?
Your eye should be level with the scale reading, viewing it perpendicular to the scale, so you can read accurately from the bottom of the meniscus.
Temperature is measured in degrees ______ (°C) and mass is measured in ______ (g) in most chemistry experiments.
Temperature is measured in degrees Celsius (°C) and mass is measured in grams (g) in most chemistry experiments.
Why is downward displacement of water not a suitable method for collecting a gas that is soluble in water?
Downward displacement of water is not suitable for a water-soluble gas because the gas dissolves into the water rather than collecting in the cylinder, giving an inaccurate volume measurement.
How should you prepare a digital balance before weighing a sample, and what should you do after placing the sample on it?
A digital balance should be tared (set to zero) before use. After placing the sample, you should allow the reading to settle before recording it to ensure an accurate measurement.
What is a solvent?
A solvent is a substance that dissolves a solute.
A ______ solution is one that contains the maximum concentration of solute dissolved in the solvent at a given temperature.
A saturated solution is one that contains the maximum concentration of solute dissolved in the solvent at a given temperature.
True or False?
The filtrate is the solid that remains in the filter paper after filtration.
False.
The filtrate is the liquid or solution that passes through the filter paper. The solid left behind is called the residue.
What is a solution?
A solution is a mixture of one or more solutes dissolved in a solvent.
Salt is ______ in water, meaning it dissolves. Sand is ______ in water, meaning it does not dissolve.
Salt is soluble in water, meaning it dissolves. Sand is insoluble in water, meaning it does not dissolve.
What is the difference between the residue and the filtrate in a filtration experiment?
The residue is the undissolved solid that remains on the filter paper.
The filtrate is the liquid or solution that passes through the filter paper into the collecting vessel.
What is the purpose of an indicator in an acid-base titration?
An indicator is used to show the endpoint of a titration by producing a sharp colour change at the exact point of neutralisation.
In a titration, the acid is added from the ______ while the exact fixed volume of alkali is measured using a ______ pipette.
In a titration, the acid is added from the burette while the exact fixed volume of alkali is measured using a volumetric pipette.
What colours does methyl orange show in acid and in alkali?
Methyl orange is red in acid and yellow in alkali.
True or False?
Litmus is the most suitable indicator for determining the endpoint in an acid-base titration.
False.
Litmus is not suitable for titrations because it does not give a sharp colour change at the endpoint. Methyl orange or phenolphthalein are preferred.
Why is a white tile placed beneath the conical flask during a titration?
A white tile is placed beneath the conical flask so that the colour change of the indicator can be seen more clearly against a pale background.
To increase accuracy, a titration should be repeated until two ______ results are obtained (within 0.1 cm3 of each other).
To increase accuracy, a titration should be repeated until two concordant results are obtained (within 0.1 cm3 of each other).
How should you add solution from the burette as you approach the endpoint of a titration?
As you approach the endpoint, you should add solution from the burette drop by drop, swirling the flask between each addition, until a single drop causes a permanent colour change in the indicator.
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