A student investigates the saponification of a triglyceride extracted from canola oil. The student aims to determine the average molecular weight of the fatty acids present in the triglyceride. The student hydrolyzes a known mass of the triglyceride with excess potassium hydroxide (KOH). After the reaction is complete, they titrate the excess KOH with a standardized hydrochloric acid (HCl) solution.
Explain how the student can use the data obtained from the titration, along with the initial mass of the triglyceride, to deduce the average molecular weight of the fatty acids in the canola oil triglyceride. Detail all necessary steps and calculations, including appropriate chemical equations and stoichiometric relationships, to justify your reasoning. What potential sources of error could affect the accuracy of the deduced molecular weight?
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Create Free Account Log inThis is a free VCE Units 3 & 4 Chemistry practice question worth 6 marks, testing your understanding of Investigation concepts. It falls under Student-designed scientific investigation in Unit 4: How are carbon-based compounds designed for purpose?. Submit your answer above to receive instant AI-powered marking and personalised feedback.
Carbon is the basis not only of the structure of living tissues but is also found in fuels, foods, medicines, polymers and many other materials that we use in everyday life. In this unit students investigate the structures and reactions of carbon-based organic compounds, including considering how green chemistry principles are applied in the production of synthetic organic compounds. They study the metabolism of food and the action of medicines in the body. They explore how laboratory analysis and various instrumentation techniques can be applied to analyse organic compounds in order to identify them and to ensure product purity. Students conduct practical investigations related to the synthesis and analysis of organic compounds, involving reaction pathways, organic synthesis, identification of functional groups, direct redox titrations, solvent extraction and distillations. Throughout the unit students use chemistry terminology including symbols, formulas, chemical nomenclature and equations to represent and explain observations and data from their own investigations and to evaluate the chemistry-based claims of others. A student-designed scientific investigation involving the generation of primary data related to the production of energy and/or chemicals and/or the analysis or synthesis of organic compounds is undertaken in either Unit 3 or Unit 4, or across both Units 3 and 4, and is assessed in Unit 4 Outcome 3. The design, analysis and findings of the investigation are presented in a scientific poster format. School-based assessment The student’s level of achievement in Unit 4 will be determined by School-assessed Coursework, which contributes 30 per cent to the study score. Students complete a set of tasks to address Outcomes 1 and 2, and design and conduct a student investigation for Outcome 3. External assessment The level of achievement for Units 3 and 4 is also assessed by an end-of-year examination contributing 50 per cent to the study score.
Students undertake a student-designed scientific investigation in either Unit 3 or Unit 4, or across both Units 3 and 4. The investigation involves the generation of primary data related to the production of energy and/or chemicals and/or the analysis or synthesis of organic compounds. The design, analysis and findings are presented in a scientific poster. Outcome 3 On completion of this unit the student should be able to design and conduct a scientific investigation related to the production of energy and/or chemicals and/or the analysis or synthesis of organic compounds, and present an aim, methodology and method, results, discussion and conclusion in a scientific poster. Key knowledge
chemical concepts specific to the selected scientific investigation and their significance, including definitions of key terms
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Define the term 'primary data' in the context of a student-designed scientific investigation.
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