Ch.1 - Introduction: Matter, Energy, and Measurement

Problem 40a

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Chapter 1, Problem 40a

a. After the label fell off a bottle containing a clear liquid believed to be a solvent called tetrahydrofuran, a chemist measured the density of the liquid to verify its identity. A 25.0-mL portion of the liquid had a mass of 22.08 g. A chemistry handbook lists the density of tetrahydrofuran at 25 °C as 0.8833 g/mL. Is the calculated density in agreement with the tabulated value?

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Calculate the density of the liquid by using the formula for density, which is Density = \( \frac{Mass}{Volume} \).

Substitute the given mass (22.08 g) and volume (25.0 mL) into the density formula.

Compare the calculated density with the tabulated density of tetrahydrofuran, which is 0.8833 g/mL.

Determine if the calculated density is close enough to the tabulated value to confirm the identity of the liquid as tetrahydrofuran.

Consider any potential experimental errors or conditions that might affect the density measurement, such as temperature variations.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Density

Density is defined as the mass of a substance divided by its volume, typically expressed in grams per milliliter (g/mL) for liquids. It is a crucial physical property that helps identify substances, as different materials have unique densities. In this scenario, the density of the liquid is calculated using the mass (22.08 g) and volume (25.0 mL) to determine if it matches the known density of tetrahydrofuran.

Measurement and Calculation

Accurate measurement and calculation are essential in chemistry for determining properties like density. The mass of the liquid is measured using a balance, while the volume is measured using a graduated cylinder. The calculated density is obtained by dividing the mass by the volume, and this value is then compared to the standard density to assess identity and purity.

Comparison with Standard Values

Comparing calculated values with standard or tabulated values is a fundamental practice in chemistry to verify the identity of substances. In this case, the calculated density of the liquid is compared to the known density of tetrahydrofuran at 25 °C (0.8833 g/mL). A close match indicates that the liquid is likely tetrahydrofuran, while significant discrepancies may suggest it is a different substance.

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Related Practice

Textbook Question

b. An experiment requires 78.1 g of benzene, a liquid whose density is 0.876 g/mL. Rather than weigh the sample on a balance, a chemist chooses to dispense the liquid using a graduated cylinder. What volume of the liquid should he use?

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Textbook Question

c. A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm³, what is the mass of the cube?

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Textbook Question

(d) A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm³, what is the mass of the cube?

b. An experiment requires 50.0 g of a substance called n-hexane, whose density at 25 °C is 0.6606 g/mL. What volume of n-hexane should be used?

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Textbook Question

The density of titanium metal is 4.506 g/cm³at 20 °C. What is the mass of a spherical ball of titanium with a diameter of 2.00 cm. [The volume of a sphere is (4/3) πr³, where r is the radius.]

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Textbook Question

For January through April 2020, at the height of the global coronavirus pandemic, it is estimated that global emissions of carbon dioxide (CO₂) decreased by 940 million metric tons (1 metric ) compared to the same period in 2019. a. Express this mass of CO₂in grams without exponential notation, using an appropriate metric prefix.

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