Practical Skills_Chemistry

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What is the precision of a thermometer reading as stated in the notes?

1 decimal place (1 d.p.).

What precision is used for time measurement with a stopwatch in these notes?

Nearest second (due to human reaction time).

To what precision is a fixed volume measured by a pipette?

1 decimal place.

What precision is used for a measuring cylinder in these notes?

1 decimal place.

Burette readings are given to how many decimal places?

2 decimal places (2 d.p.).

What are key requirements for plotting a graph according to the notes?

Plot neatly with a sharp pencil, avoid double lines, and use crosses for data points.

How much of the graph paper should the plotted graph cover?

Cover more than half the graph paper.

What is a suggested example of scale on a graph?

A suggested scale is 2, 4, 5, or 10 units per 2 cm.

Which axis is used for the independent (changed) variable on the graph?

X-axis.

Which axis is used for the dependent (measured) variable, and what information should be included on the axes?

The Y-axis is used for the dependent variable; both axes should be labelled with units.

What should the graph title describe?

A brief description of the experiment, e.g., 'Graph of the dependent variable against the independent variable'.

What symbol should be used to plot data points?

Crosses.

What is the required plotting precision for data points on the graph?

Data points should be plotted within half a small square (e.g., 2.52 plotted at 2.50).

What is a requirement for the best-fit line on a graph?

The best-fit line should have an equal number of points on both sides.

When recording observations for a gas produced, what details should be noted?

Effervescence, the gas's color and smell, its respective gas test, and the gas itself.

In the example, what are the properties (color and odor) of the gas produced?

It is a colorless and odorless gas.

How can hydrogen gas be identified through observations?

Hydrogen gas extinguishes a lighted splint with a 'pop' sound.

How is a color change recorded in observations?

The initial color turns into the final color.

What observation is recorded when a precipitate forms?

The color of the precipitate.

If a precipitate is soluble in excess aqueous solution, what should be noted?

It dissolves to produce a colored solution.

What does it mean if a precipitate is insoluble in excess aqueous solution?

The precipitate remains insoluble.

What is a common source of error related to timing in rate studies?

Human reaction time error, leading to inaccurate time measurement.

What error can occur from not cutting magnesium ribbons to the exact length?

Inconsistent ribbon size or length, leading to differences in reaction rates.

In enthalpy change experiments, what causes temperature readings to be lower than expected?

Heat loss to the surroundings.

What effect does a slow run of acid from the burette have on temperature readings?

More heat loss to the surroundings before taking temperature readings.

In titration, what error affects the endpoint if more than one drop is added?

Inaccurate determination of the endpoint due to adding more than one drop.

If the burette is not washed with the reactant before starting, how is the calculated concentration affected?

The calculated concentration will be higher or lower due to contamination, as both the volume needed to reach the endpoint and the calculated moles will be affected.

What variable is directly affected if the burette is not washed before titration?

The concentration or volume of the solution is directly affected, leading to incorrect calculations.