Q: A scientist needs to convert 3.5 weeks into seconds. Which sequence of conversion factors should be used?

$$3.5 \text{ weeks} \times \frac{7 \text{ days}}{1 \text{ week}} \times \frac{24 \text{ hours}}{1 \text{ day}} \times \frac{60 \text{ min}}{1 \text{ hour}} \times \frac{60 \text{ s}}{1 \text{ min}}$$

Question 1

Which of the following best describes the difference between an exact number and a measured number in chemistry?

Accepted Answer

An exact number is obtained by counting or definition and has no uncertainty, while a measured number is obtained using instruments and always contains some uncertainty.

Question 2

A student measures the length of a table four times and records: 120.1 cm, 120.2 cm, 120.0 cm, and 120.1 cm. The actual length is 119.8 cm. Which statement is correct about the student’s measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Why do measured numbers always have uncertainty?

Accepted Answer

Because the last digit is estimated based on the instrument’s limitations.

Question 4

How many significant figures are in the measurement 0.001020 g?

Accepted Answer

Four

Question 5

Convert $$4.68 	imes 10$$^{-1}$$ to standard notation.

Accepted Answer

$$0.468$$

Question 6

Which of the following numbers has the greatest degree of uncertainty?

Accepted Answer

600

Question 7

When multiplying $$2.0 cm by$$ $$2 cm$$, what is the correct answer with the proper number of significant figures?

Accepted Answer

$$4 cm$^2$$

Question 8

A cube has sides of $$10.0 mm $$and a mass of $$4.70 g. $$What is its density in $$g/cm^3$$?

Accepted Answer

$$0.047 g/cm$^3$$

Question 9

Which of the following is a derived SI unit?

Accepted Answer

Cubic meter ($$m^3)$$

Question 10

What is the mass, in kilograms, of $$500.0 L of $$air if the density of air is $$0.00130 g/mL$$?

Accepted Answer

$$0.650 kg$$

Question 11

Which of the following is the correct equation for calculating the amount of heat energy absorbed or released?

Accepted Answer

$$q = mC(T_f - T_i)$$

Question 12

A sample of water is heated from $$25.0^{\circ}C$ to 45.0$$^{\circ}$$C$$ using $$1.00 	imes 10^4$ g of water. How much energy (in calories) is absorbed? (Specific heat of water = 1.00$ cal/g$$\$$cdot^{\circ}C)$$

Accepted Answer

$$2.00 	imes 10^5$ cal

Question 13

Which of the following is an intensive property?

Accepted Answer

Density

Question 14

Convert $$0.025 m to $$millimeters.

Accepted Answer

$$25 mm$$

Question 15

Which of the following can be used as a conversion factor?

Accepted Answer

$$4.184 J$$/$$^{\circ}C$$

Question 16

What is the correct way to rearrange the density equation $$d = \frac{m}{V} to $$solve for mass ($$m$$)?

Accepted Answer

$$m = d 	imes V$$

Question 17

A temperature is measured as $$68^{\circ}F. $$What is this temperature in $$^{\circ}C$$? (Use $$^{\circ}C$$ = $$\frac{5}{9}$$(^{\circ}$$F $$-$$ 32)$)

Accepted Answer

$$20^{\circ}C$$

Question 18

Which of the following best explains why trailing zeros in a number like 120. are significant?

Accepted Answer

Because the decimal point indicates that the zeros are measured and not just placeholders.

Question 19

A scientist needs to convert 3.5 weeks into seconds. Which sequence of conversion factors should be used?

Accepted Answer

$$3.5 	ext{ weeks} 	imes \frac{7 	ext{ days}}{1 	ext{ week}} 	imes \frac{24 	ext{ hours}}{1 	ext{ day}} 	imes \frac{60 	ext{ min}}{1 	ext{ hour}} 	imes \frac{60 	ext{ s}}{1 	ext{ min}}$$

Chapter 2: The Numerical Side of Chemistry – Precision, Accuracy, and Measurement

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