AS Chemistry₇₄₀₄

MS 0.0

Recognise and make use of appropriate units in calculation

Students may be tested on their ability to:

• convert between units, eg cm³ to dm³ as part of volumetric calculations
• give units for an equilibrium constant or a rate constant
• understand that different units are used in similar topic areas, so that conversions may be necessary, eg entropy in J mol^–1 K^–1 and enthalpy changes in kJ mol^–1 .

MS 0.1

Recognise and use expressions in decimal and ordinary form

Students may be tested on their ability to:

• use an appropriate number of decimal places in calculations, eg for pH
• carry out calculations using numbers in standard and ordinary form, eg use of Avogadro’s number
• understand standard form when applied to areas such as (but not limited to) K _w
• convert between numbers in standard and ordinary form
• understand that significant figures need retaining when making conversions between standard and ordinary form, eg 0.0050 mol dm^–3 is equivalent to 5.0 × 10^–3 mol dm^–3 .

MS 0.2

Use ratios, fractions and percentages

Students may be tested on their ability to:

• calculate percentage yields
• calculate the atom economy of a reaction
• construct and/or balance equations using ratios.

MS 0.3

Estimate results

Students may be tested on their ability to:

• evaluate the effect of changing experimental parameters on measurable values, eg how the value of K _c would change with temperature given different specified conditions.

MS 0.4

Use calculators to find and use power, exponential and logarithmic functions

Students may be tested on their ability to:

• carry out calculations using the Avogadro constant
• carry out pH and p K _a calculations
• make appropriate mathematical approximations in buffer calculations .

MS 1.1

Use an appropriate number of significant figures

Students may be tested on their ability to:

• report calculations to an appropriate number of significant figures, given raw data quoted to varying numbers of significant figures
• understand that calculated results can only be reported to the limits of the least accurate measurement.

MS 1.2

Find arithmetic means

Students may be tested on their ability to:

• calculate weighted means, eg calculation of an atomic mass based on supplied isotopic abundances
• select appropriate titration data (ie identification of outliers) in order to calculate mean titres.

MS 1.3

Identify uncertainties in measurements and use simple techniques to determine uncertainty when data are combined

Students may be tested on their ability to:

• determine uncertainty when two burette readings are used to calculate a titre value.

MS 2.1

Understand and use the symbols: =, <, <<, >>, >, $\mathsf{\propto }$ , ~, equilibrium sign

No exemplification required.

MS 2.2

Change the subject of an equation

Students may be tested on their ability to:

• carry out structured and unstructured mole calculations, eg calculate a rate constant k from a rate equation .

MS 2.3

Substitute numerical values into algebraic equations using appropriate units for physical quantities

Students may be tested on their ability to:

• carry out structured and unstructured mole calculations
• calculate the value of an equilibrium constant K _c .
• carry out rate calculations

MS 2.4

Solve algebraic equations

Students may be tested on their ability to:

• carry out Hess’s law calculations
• calculate a rate constant k from a rate equation .

MS 2.5

Use logarithms in relation to quantities that range over several orders of magnitude

Students may be tested on their ability to:

• carry out pH and p K _a calculations .

MS 3.1

Translate information between graphical, numerical and algebraic forms

Students may be tested on their ability to:

• interpret and analyse spectra
• determine the order of a reaction from a graph
• derive a rate expression from a graph .

MS 3.2

Plot two variables from experimental or other data

Students may be tested on their ability to:

• plot concentration–time graphs from collected or supplied data and draw an appropriate best-fit curve.

MS 3.3

Determine the slope and intercept of a linear graph

Students may be tested on their ability to:

• calculate the rate constant of a zero-order reaction by determination of the gradient of a concentration–time graph .

MS 3.4

Calculate rate of change from a graph showing a linear relationship

Students may be tested on their ability to:

• calculate the rate constant of a zero-order reaction by determination of the gradient of a concentration–time graph .

MS 3.5

Draw and use the slope of a tangent to a curve as a measure of rate of change

Students may be tested on their ability to:

• determine the order of a reaction using the initial rates method .

MS 4.1

Use angles and shapes in regular 2D and 3D structures

Students may be tested on their ability to:

• predict/identify shapes of and bond angles in molecules with and without a lone pair(s), for example NH₃ , CH₄ , H₂ O etc.

MS 4.2

Visualise and represent 2D and 3D forms including two-dimensional representations of 3D objects

Students may be tested on their ability to:

• draw different forms of isomers
• identify chiral centres from a 2D or 3D representation .

MS 4.3

Understand the symmetry of 2D and 3D shapes

Students may be tested on their ability to:

• describe the types of stereoisomerism shown by molecules/complexes
• identify chiral centres from a 2D or 3D representation .