A Phosphate Buffer Solution (25

question 65

Multiple Choice

A phosphate buffer solution (25.00 mL sample) used for a growth medium was titrated with 0.1000 M hydrochloric acid. The components of the buffer were sodium monohydrogenphosphate and sodium dihydrogenphosphate. The first endpoint occurred at a volume of 10.32 mL; the second occurred after an additional 18.62 mL was added (or total volume = 28.94 mL) . What was the approximate ratio of HPO₄^2- to H₂PO₄^- in the buffer?

• A) 1:1
• B) 4:5
• C) 5:3
• D) 5:4
• E) 3:5

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Definitions:

Controllable Margin

A measure of profitability that focuses on the income and expenses directly controlled by a manager or business unit, excluding fixed costs.

Fixed Costs

Expenses that do not change with the level of production or sales activities over a relevant period.

Contribution Margin

The difference between sales revenue and variable costs, indicating the amount contributed towards covering fixed costs and generating profit.

Performance Reports

Documents that review and assess the performance of individuals, departments, or organizations against planned objectives.