Q: A wooden block with dimensions 0.15 m × 0.44 m × 0.56 m is floating on a lake. If it is submerged by 0.031 m, what is its mass? (Density of water = 1.00 g/mL)

Mass = $$0.15 \times 0.44 \times 0.56 \times 0.031 \times 1000 kg$$

Q: A small crystal of sucrose (C$$_{12}H$_{22}O$_{11}) $$has a mass of 5.345 mg and dimensions 2.20 mm × 1.36 mm × 1.12 mm. What is its density in g/mL?

Density = $$\frac{5.345 \times 10$$^{-3}$$}{2.20 \times 1.36 \times 1.12 \times 10$$^{-3}$$} g/mL$$

Q: A 39.0 g piece of aluminum metal has a volume of 14.4 cm$$^3. $$What is the apparent weight of the piece when immersed in chloroform at 25°C ($$\rho = 1.49 g/cm$^3$$)?

Apparent weight = $$39.0 - (1.49 \times 14.4) g$$

Q: A container weighing 73.190 g is filled with an unknown liquid. The combined mass is 87.308 g. The container is then emptied and filled with water, recording a mass of 88.442 g at 19°C ($$d = 1.0027 g/mL). $$What is the density of the unknown liquid?

Density = $$\frac{87.308 - 73.190}{88.442 - 73.190} \times 1.0027 g/mL$$

Q: A piece of concrete weighs 120 N. When fully submerged, its apparent weight is 97 N. If the volume of water displaced is 4200 cm$$^3$$ ($$g = 9.8 N/kg$$), what is the density of water?

Density = $$\frac{120 - 97}{4200 \times 9.8} g/mL$$

Question 1

Which color on the chemical hazard diamond represents the fire hazard, and what does a rating of 4 in this section indicate?

Accepted Answer

Red; rating of 4 means the chemical has a flash point below 23°C and is extremely flammable.

Question 2

A scientist needs to deliver exactly 25.0 mL of a solution for a titration. Which apparatus should be used for the highest accuracy?

Accepted Answer

Transfer pipet

Question 3

When weighing an analyte, why must buoyancy be considered, and which equation corrects for it?

Accepted Answer

Buoyancy causes the object to appear lighter; the correction equation is $$m' \left(1 - \frac{d_a}{d}\right) \div \left(1 - \frac{d_a}{d_w}\right).$$

Question 4

A wooden block with dimensions 0.15 m × 0.44 m × 0.56 m is floating on a lake. If it is submerged by 0.031 m, what is its mass? (Density of water = 1.00 g/mL)

Accepted Answer

Mass = $$0.15 	imes 0.44 	imes 0.56 	imes 0.031 	imes 1000 kg$$

Question 5

Which laboratory apparatus is best suited for separating a solid from a liquid by filtration?

Accepted Answer

Buchner funnel

Question 6

A small crystal of sucrose (C$$_{12}H$_{22}O$_{11}) $$has a mass of 5.345 mg and dimensions 2.20 mm × 1.36 mm × 1.12 mm. What is its density in g/mL?

Accepted Answer

Density = $$\frac{5.345 	imes 10$$^{-3}$$}{2.20 	imes 1.36 	imes 1.12 	imes 10$$^{-3}$$} g/mL$$

Question 7

Which process is used to measure the actual quantity of mass, volume, and other chemical measurements that relate to what we observe on an analytical scale?

Accepted Answer

Calibration

Question 8

A 39.0 g piece of aluminum metal has a volume of 14.4 cm$$^3. $$What is the apparent weight of the piece when immersed in chloroform at 25°C ($$\rho = 1.49 g/cm$^3$$)?

Accepted Answer

Apparent weight = $$39.0 - (1.49 	imes 14.4) g$$

Question 9

Which apparatus is used to accurately measure and transfer small volumes of liquid in analytical chemistry?

Accepted Answer

Volumetric pipet

Question 10

During filtration, what is the term for the material left behind on the filter paper?

Accepted Answer

Residue

Question 11

A solution is prepared at 21°C with a density of 0.9979655 g/mL. If the same solution is measured at 26°C with a density of 0.9967867 g/mL, what happens to the molarity?

Accepted Answer

Molarity decreases as temperature increases.

Question 12

What is the formula for calculating the buoyant force acting on an object submerged in a liquid?

Accepted Answer

$$F = \rho V g$$

Question 13

A container weighing 73.190 g is filled with an unknown liquid. The combined mass is 87.308 g. The container is then emptied and filled with water, recording a mass of 88.442 g at 19°C ($$d = 1.0027 g/mL). $$What is the density of the unknown liquid?

Accepted Answer

Density = $$\frac{87.308 - 73.190}{88.442 - 73.190} 	imes 1.0027 g/mL$$

Question 14

Which apparatus is used for the separation of immiscible liquids in an extraction process?

Accepted Answer

Separatory funnel

Question 15

What is the main purpose of using a volumetric flask in analytical chemistry?

Accepted Answer

To prepare solutions of precise volume

Question 16

Which correction must be applied when measuring the volume of a solution at temperatures different from 20°C?

Accepted Answer

Thermal expansion correction: $$\frac{c'}{d'} = \frac{c}{d}$$

Question 17

A piece of concrete weighs 120 N. When fully submerged, its apparent weight is 97 N. If the volume of water displaced is 4200 cm$$^3$$ ($$g = 9.8 N/kg$$), what is the density of water?

Accepted Answer

Density = $$\frac{120 - 97}{4200 	imes 9.8} g/mL$$

Question 18

Which laboratory technique separates a solute from a solvent based on boiling point differences?

Accepted Answer

Evaporation

Question 19

If a solution is diluted 100-fold, how is this achieved?

Accepted Answer

99 parts solvent to 1 part solution

Fundamental Laboratory Techniques and Measurements in Analytical Chemistry

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