use a range of materials and glassware to perform a volumetric analysis (to verify that vinegar concentrations match that on the bottle
SACE Stage Two Chemistry Investigations Folio Practical Investigation – Volumetric Analysis Cover Sheet SACE Registration Number: School Number: Description of Assessment Students use a range of materials and glassware to perform a volumetric analysis (to verify that vinegar concentrations match that on the bottle). Students demonstrate their ability to: · select glassware appropriate to the task · use volumetric glassware correctly · convert units to estimate a dilution from claim on container · accurately dilute a solution · perform a titration · calculate acid concentration for each vinegar bottle and use these to form a conclusion · discuss accuracy and precision of their results · evaluate the procedure and the impact of sources of systematic and random error. Assessment Conditions Time allocation: 100 min practical. The practical is completed under supervision. Purpose: To verify the concentration claim on the bottle for two vinegar brands. Materials provided: · · 50 mL each of two vinegar samples · 150 mL standardised NaOH solution (0.100mol L-1) · phenolphthalein · volumetric pipettes (10.0, 20.0, 25.0 mL available) · volumetric flasks (100.0, 200.0, 250.0, 500.0 mL available) · 250 mL conical flasks · burette · burette funnel · white tile · retort stand and clamp · pipette filler Procedure: Part A: Dilution of the vinegar samples · Convert the vinegar concentrations from the bottle from %w/v to mol L-1 and use this and a chemical equation to explain why a dilution of factor of 10 is appropriate for each vinegar sample · In partners, dilute two different brands of vinegar (one each) in an appropriate fashion. Part B: Titration of NaOH solution with the vinegar solutions · Separately, titrate the sodium hydroxide solution in the burette with the diluted acids in the conical flask, using phenolphthalein as the indicator. Result Practical Report Prepare a Practical report that includes: 1. Introduction of the science of titrations and your investigable question. 2. Calculations converting units for vinegar concentrations and therefore a statement of how dilutions will be conducted based on these calculations. 3. A table of results from titration. 4. Calculations to show concentrations for each undiluted vinegar sample. 5. A discussion that: · Describes the outcome of results compared to claims from bottles. · Explains the rinsing procedures and reasons, for all equipment used. · Discusses random and systematic error including any suggested improvements in procedure. · Make a valid conclusion including a summary of precision and accuracy of results. Refer to the marks scheme which has the criteria for judging performance for an indication of what is required and the depth of treatment for each part of your report. Volumetric Analysis Practical IAE2 IAE4 IAE3 KA2 KA4 Evidence required · Table of values · Concordance of titres – within 0.1 mL · Accuracy of result · Appropriate use of equipment and selection of glassware · Random and Systematic error discussion · Improvements if appropriate · Discussion of what calculations show about vinegar concentrations · Conclusion including validity and reliability of conclusion · Calculations: · Unit conversion for Dilution · Concentration of vinegar from results · Chemical equation · Introduction · Explanation of rinsing procedures · Logical structure and formatting · Within word count · Appropriate chemical terminology used · Appropriate sig. figs A Obtains records, and represents data, using appropriate conventions and formats accurately and highly effectively. Critically and logically evaluates procedures and discusses their effect on data. Systematically analyses and interprets data and evidence to formulate logical conclusions with detailed justification. Develops and applies chemical concepts highly effectively in new and familiar contexts. Communicates knowledge and understanding of chemistry coherently, with highly effective use of appropriate terms, conventions, and representations. B Obtains, records, and represents data, using appropriate conventions and formats mostly accurately and effectively. Logically evaluates procedures and their effect on data. Logically analyses and interprets data and evidence to formulate suitable conclusions with reasonable justification. Develops and applies chemical concepts mostly effectively in new and familiar contexts. Communicates knowledge and understanding of chemistry mostly coherently, with effective use of appropriate terms, conventions, and representations. C Obtains, records, and represents data, using generally appropriate conventions and formats with some errors but generally accurately and effectively. Evaluates procedures and some of their effect on data. Undertakes some analysis and interpretation of data and evidence to formulate generally appropriate conclusions with some justification. Develops and applies chemical concepts generally effectively in new or familiar contexts. Communicates knowledge and understanding of chemistry generally effectively, using some appropriate terms, conventions, and representations. D Obtains, records, and represents data, using conventions and formats inconsistently, with occasional accuracy and effectiveness. Attempts to evaluate procedures or suggest an effect on data. Describes data and undertakes some basic interpretation to formulate a basic conclusion. Develops and applies some chemical concepts in familiar contexts. Communicates basic chemical information, using some appropriate terms, conventions, and/or representations. E Attempts to record and represent some data with limited accuracy or effectiveness. Acknowledges that procedures affect data. Attempts to describe results and/or interpret data to formulate a basic conclusion. Attempts to develop and apply chemical concepts in familiar contexts. Attempts to communicate information about chemistry. I No evidence No evidence No evidence No evidence No evidence Score /15 /10 /10 /15 /15 Checklist SACE ID: Task Comment Teacher initials Safety glasses and general safety Pipette rinsed correctly Volumetric flask and conical flask rinsed correctly Burette rinsed correctly Pipette filled correctly Volumetric flask filled correctly Dilution performed correctly Indicator added correctly Titration performed correctly Concordant titres Accuracy