-SQA- SCOTTISH QUALIFICATIONS AUTHORITY HIGHER NATIONAL UNIT SPECIFICATION GENERAL INFORMATION PHYSICAL CHEMISTRY: PHASE EQUILIBRIUM

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1 -SQA- SCOTTISH QUALIFICATIONS AUTHORITY GENERAL INFORMATION -Unit Number Superclass- -Title- RD DESCRIPTION- GENERAL COMPETENCE FOR UNIT: Applying Raoult's Law to colligative properties and using the phase rule and phase diagrams to describe two component condensed systems. OUTCOMES 1. apply Raoult's law to colligative properties; 2. use the phase rule and phase diagrams to describe two component condensed systems. CREDIT VALUE: 0.5 HN Credit ACCESS STATEMENT: The successful completion of the HN unit Concepts in Physical Chemistry or equivalent For further information contact: Committee and Administration Unit, SQA, Hanover House, 24 Douglas Street, Glasgow G2 7NQ. Additional copies of this unit may be purchased from SQA (Sales and Despatch section). At the time of publication, the cost is 1.50 (minimum order 5.00).

2 STATEMENT OF STANDARDS UNIT NUMBER: UNIT TITLE: Acceptable performance in this unit will be the satisfactory achievement of the standards set out in this part of the specification. All sections of the statement of standards are mandatory and cannot be altered without reference to SQA. OUTCOME 1. APPLY RAOULT'S LAW TO COLLIGATIVE PROPERTIES PERFORMANCE CRITERIA The descriptions of colligative properties are correct. The calculations of the effect of non-volatile solutes on properties of solvents are correct. RANGE STATEMENT Properties: vapour pressure; elevation of boiling point; depression of freezing point; osmotic pressure. EVIDENCE REQUIREMENTS Written evidence of the ability to describe colligative properties and calculate the effect of non-volatile solutes on properties of solvents. One calculation must include the effect of association or dissociation. OUTCOME 2. USE THE PHASE RULE AND PHASE DIAGRAMS TO DESCRIBE TWO COMPONENT CONDENSED SYSTEMS PERFORMANCE CRITERIA The construction of a phase diagram using cooling curve data is correct. The interpretation of a phase diagram is correct in terms of the phase rule and the tie-line principle. 2

3 RANGE STATEMENT The range statement for this outcome is specified within the performance criteria. EVIDENCE REQUIREMENTS Written and graphical evidence of the ability to construct and interpret a phase diagram. MERIT A candidate will be awarded a pass with merit it he/she meets the conditions for a pass and in so doing can demonstrate superior performance in all outcomes of the unit. Superior performance might be demonstrated by, for example: giving a fuller and more in-depth description of colligative properties; giving an interpretation of a phase diagram which shows a more in-depth understanding of the phase rule and the tie-line principle ASSESSMENT In order to achieve this unit, candidates are required to present sufficient evidence that they have met all the performance criteria for each outcome within the range specified. Details of these requirements are given for each outcome. The assessment instruments used should follow the general guidance offered by the SQA assessment model and an integrative approach to assessment is encouraged. (See references at the end of support notes). Accurate records should be made of the assessment instruments used showing how evidence is generated for each outcome and giving marking schemes and/or checklists, etc. Records of candidates' achievements should also be kept. These records will be required for external verification. SPECIAL NEEDS Proposals to modify outcomes, range statements or agreed assessment arrangements should be discussed in the first place with the external verifier. Copyright SQA 1996 Please note that this publication may be reproduced in whole or in part for educational purposes provided that: (i) (ii) no profit is derived from the reproduction; if reproduced in part, the source is acknowledged. 3

4 SUPPORT NOTES UNIT NUMBER: UNIT TITLE: SUPPORT NOTES: This part of the unit specification is offered as guidance. None of the sections of the support notes is mandatory. NOTIONAL DESIGN LENGTH: SQA allocates a notional design length to a unit on the basis of the time estimated for achievement of the stated standards by a candidate whose starting point is as described in the access statement. The notional design length for this unit is 20 hours. The use of notional design length for programme design and timetabling is advisory only. PURPOSE This unit will enable the candidate to develop an understanding of phase equilibrium. This unit would be suitable as part of a Higher National course and for those wishing to gain a degree of the underpinning knowledge requirements of the SVQ in laboratory operations. CONTENT/CONTEXT Corresponding to outcomes: Outcome 1 Outcome 2 Raoult s Law. Lowering of vapour pressure of a liquid by a nonvolatile solute. Elevation of boiling point and depression of freezing point for solutions. Molality. Osmosis, semi-permeable membranes. Osmotic pressure of solutions. Calculations for each colligative property. Effects of association and dissociation. The phase rule. Phase diagrams for two component condensed systems. Tie lines. Phase diagram for system forming a eutectic Calculations involving the phase rule and tie lines. REFERENCES 1. Guide to unit writing. 2. For a fuller discussion on assessment issues, please refer to SQA's Guide to Assessment. 3. Information for centres on SQA's operating procedures is contained in SQA's Guide to Procedures. 4. For details of other SQA publications, please consult SQA's publications list. 4

5 Copyright SQA 1996 Please note that this publication may be reproduced in whole or in part for educational purposes provided that: (i) (ii) no profit is derived from the reproduction; if reproduced in part, the source is acknowledged. 5