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Questions and Answers
What term describes the compound that is formed by the reaction of a reagent from a solution in gravimetric analysis?
What term describes the compound that is formed by the reaction of a reagent from a solution in gravimetric analysis?
What condition indicates that a solution of lead sulphate is supersaturated?
What condition indicates that a solution of lead sulphate is supersaturated?
Which of the following statements correctly explains the effect of using an equivalent amount of precipitant during precipitation?
Which of the following statements correctly explains the effect of using an equivalent amount of precipitant during precipitation?
According to the first solubility product rule, what must occur for a precipitate to form?
According to the first solubility product rule, what must occur for a precipitate to form?
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What is the value of the solubility product (SP) for lead sulfate at 25°C?
What is the value of the solubility product (SP) for lead sulfate at 25°C?
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To achieve more complete precipitation of Pb++, what must be done with the concentration of SO4-- ions?
To achieve more complete precipitation of Pb++, what must be done with the concentration of SO4-- ions?
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Which of the following is NOT a characteristic of desiccators?
Which of the following is NOT a characteristic of desiccators?
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What consequence follows if the concentration of [Pb++][SO4--] is less than the solubility product?
What consequence follows if the concentration of [Pb++][SO4--] is less than the solubility product?
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Which statement describes the relationship between the product of the concentrations of the ions and the solubility product in a concentrated solution?
Which statement describes the relationship between the product of the concentrations of the ions and the solubility product in a concentrated solution?
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What must be understood about the different forms in gravimetric analysis?
What must be understood about the different forms in gravimetric analysis?
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Study Notes
Gravimetric Analysis
- Distinction between precipitated and weighed forms:
- Precipitated form: Compound precipitated from solution.
- Weighed form: Compound weighed to determine final result.
Solubility Product (SP)
- Saturated solution: Ions' product reaches a constant value (Solubility Product) at a given temperature.
- Example (PbSO₄ at 25°C): [Pb²⁺][SO₄²⁻] = 2.2 × 10⁻⁸
- Unsaturated solution: [Pb²⁺][SO₄²⁻] < 2.2 × 10⁻⁸ (more PbSO₄ can dissolve)
- Supersaturated solution: [Pb²⁺][SO₄²⁻] > 2.2 × 10⁻⁸ (some PbSO₄ must precipitate)
- Solubility Product Rule 1: Precipitate forms when ion product exceeds SP.
Effect of Excess Precipitant
- Incomplete precipitation with equivalent amounts.
- More complete precipitation with excess precipitant .
- Solubility Product Rule 2: Ion product in concentrated solution equals SP.
- Higher precipitant concentration reduces ion concentration (to precipitate more completely).
Desiccators
- Use: Storage and final drying of moisture-sensitive solids.
- Materials: Plastic, glass, or metal.
- Function: Maintains dry environment (not drying the material directly).
- Applications: Electronics, pharmaceuticals, optics, etc.
- Desiccating agent: Absorbent material (e.g., concentrated sulfuric acid, calcium chloride) - needs replenishing.
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Description
This quiz covers the concepts of gravimetric analysis, including the distinction between precipitated and weighed forms, as well as the solubility product equilibrium. Additionally, it addresses the effects of excess precipitant on precipitation completeness and outlines desiccator use. Test your understanding of these important analytical chemistry concepts.
