Q: A piece of platinum has a density of $$21.5\ g/cm^3$ and a volume of 4.49$$\ $$cm^3. $$What is its mass in grams?

$$m = d \times V = 21.5\ g/cm^3$ \times 4.49\ cm^3$ = 96.5\ g$$

Q: A student records the following measurements: 6.64 cm, 6.68 cm, and 6.70 cm. What is the average, and how many significant figures should it be reported with?

$$\text{Average} = \frac{6.64 + 6.68 + 6.70}{3} = 6.6733\ \rightarrow\ 6.67\ \text{cm (3 significant figures)}$$

Q: A 325-mg aspirin tablet has a mass of how many grams?

$$325\ mg \times \frac{1\ g}{1000\ mg} = 0.325\ g$$

Q: A sample of mercury has a density of $$13.6\ g/cm^3$. What is the mass in grams of 95$$\ mL$$ of mercury? (Assume 1$$\ mL = 1\ $$cm^3)$$

$$m = 13.6\ g/cm^3$ \times 95\ cm^3$ = 1292\ g$$

Q: Which of the following conversions is correct for converting $$55\ mi/hr to$$ $$m/s$$? ($$1\ mi = 1609\ m$$, $$1\ hr = 3600\ s)$$

$$55\ mi/hr \times \frac{1609\ m}{1\ mi} \times \frac{1\ hr}{3600\ s} = 24.6\ m/s$$

Q: Which of the following is the correct relationship for converting Celsius to Fahrenheit?

$$^\circ F = 1.8 \times (^\circ C) + 32$$

Question 1

A NASA spacecraft failed because engineers entered data in English units (pound·seconds) instead of metric units (Newton·seconds). Which of the following best explains why this mistake led to mission failure?

Accepted Answer

The conversion between English and metric units was not properly accounted for, leading to incorrect calculations of force and trajectory.

Question 2

Which of the following is the correct SI base unit for measuring the amount of substance?

Accepted Answer

mol

Question 3

A student measures the mass of a sample as 0.00801008 g. How many significant figures does this measurement have?

Accepted Answer

6

Question 4

Which of the following numbers has exactly three significant figures?

Accepted Answer

0.0420

Question 5

Convert a temperature of 25.0 °C to Kelvin using the correct formula.

Accepted Answer

$$T(K) = 25.0 + 273.15 = 298.15\ K$$

Question 6

A piece of platinum has a density of $$21.5\ g/cm^3$ and a volume of 4.49$$\ $$cm^3. $$What is its mass in grams?

Accepted Answer

$$m = d 	imes V = 21.5\ g/cm^3$ 	imes 4.49\ cm^3$ = 96.5\ g$$

Question 7

Which of the following statements about significant figures is correct?

Accepted Answer

Zeros at the end of a number are significant only if there is a decimal point.

Question 8

A student records the following measurements: 6.64 cm, 6.68 cm, and 6.70 cm. What is the average, and how many significant figures should it be reported with?

Accepted Answer

$$	ext{Average} = \frac{6.64 + 6.68 + 6.70}{3} = 6.6733\ ightarrow\ 6.67\ 	ext{cm (3 significant figures)}$$

Question 9

Which of the following is an example of an intensive property?

Accepted Answer

Density

Question 10

A 325-mg aspirin tablet has a mass of how many grams?

Accepted Answer

$$325\ mg 	imes \frac{1\ g}{1000\ mg} = 0.325\ g$$

Question 11

Which of the following best describes the First Law of Thermodynamics?

Accepted Answer

Energy of the universe is conserved; it cannot be created or destroyed, only transformed.

Question 12

A sample of mercury has a density of $$13.6\ g/cm^3$. What is the mass in grams of 95$$\ mL$$ of mercury? (Assume 1$$\ mL = 1\ $$cm^3)$$

Accepted Answer

$$m = 13.6\ g/cm^3$ 	imes 95\ cm^3$ = 1292\ g$$

Question 13

Which of the following conversions is correct for converting $$55\ mi/hr to$$ $$m/s$$? ($$1\ mi = 1609\ m$$, $$1\ hr = 3600\ s)$$

Accepted Answer

$$55\ mi/hr 	imes \frac{1609\ m}{1\ mi} 	imes \frac{1\ hr}{3600\ s} = 24.6\ m/s$$

Question 14

Which of the following is the correct relationship for converting Celsius to Fahrenheit?

Accepted Answer

$$^\circ F = 1.8 	imes (^\circ C) + 32$$

Question 15

A student multiplies $$5.2 	imes 12.054 	imes 0.53$$ and gets $$33.18708. $$How should the answer be reported with the correct number of significant figures?

Accepted Answer

$$6.7 (2 $$significant figures)

Question 16

Which of the following best describes an endothermic process?

Accepted Answer

Heat transfers from the surroundings to the system, increasing the system's energy.

Question 17

Which of the following is the correct scientific notation for the number 0.0000000000000000000000199?

Accepted Answer

$$1.99 	imes 10$$^{-23}$$

Question 18

Which of the following is the correct conversion factor for $$1\ km to$$ $$m$$?

Accepted Answer

$$1\ km = 1000\ m$$

Essentials of Units, Measurements, and Problem Solving in General Chemistry

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