Q: A student needs to convert 0.0056 meters to micrometers. Which calculation is correct?

$$0.0056 \times 10^6$ = 5600$$ \mu m

Q: A student measures the mass of a liquid as 25.0 g and its volume as 20.0 mL. The accepted density is 1.20 g/mL. What is the percent error in the student's measurement?

$$\%\text{ error} = \frac{1.25 - 1.20}{1.20} \times 100 = 4.17\%$$

Q: A photon has a wavelength of $$500 \text{ nm}. $$What is its energy in joules? (Use $$h = 6.63 \times 10$$^{-34}$$ \text{ J} \cdot \text{s}$$ and $$c = 3.00 \times 10^8$ \text{ m/s})$$

$$E = \frac{hc}{\lambda} = \frac{6.63 \times 10$$^{-34}$$ \times 3.00 \times 10^8$}{500 \times 10$$^{-9}$$} = 3.98 \times 10$$^{-19}$$ \text{ J}$$

Q: What is the frequency of light with a wavelength of $$600 \text{ nm}$$? (Use $$c = 3.00 \times 10^8$ \text{ m/s})$$

$$\nu = \frac{c}{\lambda} = \frac{3.00 \times 10^8$}{600 \times 10$$^{-9}$$} = 5.00 \times 10$$^{14}$$ \text{ Hz}$$

Question 1

Which of the following numbers has the correct number of significant figures according to the rules for significant figures?

Accepted Answer

1.2300 has 5 significant figures.

Question 2

A student measures the mass of a sample as 12.34 g and its volume as 4.56 mL. What is the density of the sample, reported with the correct number of significant figures?

Accepted Answer

$$d = \frac{12.34}{4.56} = 2.71 g/mL$$

Question 3

Which laboratory glassware is generally considered the most precise for measuring volume?

Accepted Answer

Volumetric flask

Question 4

A student needs to convert 0.0056 meters to micrometers. Which calculation is correct?

Accepted Answer

$$0.0056 	imes 10^6$ = 5600$$ \mu m

Question 5

Which statement best describes the difference between accuracy and precision?

Accepted Answer

Accuracy is how close measurements are to the true value; precision is how close measurements are to each other.

Question 6

A balance gives readings of 12.345 g, 12.346 g, and 12.344 g for the same object. What can be said about the precision and accuracy of the balance?

Accepted Answer

The balance is precise but may not be accurate.

Question 7

A student measures the mass of a liquid as 25.0 g and its volume as 20.0 mL. The accepted density is 1.20 g/mL. What is the percent error in the student's measurement?

Accepted Answer

$$\%	ext{ error} = \frac{1.25 - 1.20}{1.20} 	imes 100 = 4.17\%$$

Question 8

Which of the following best describes the meniscus in a graduated cylinder?

Accepted Answer

The meniscus is the lowest point of the liquid curve, and measurements are read at this point.

Question 9

Which SI unit and abbreviation correctly matches the quantity 'mass'?

Accepted Answer

Kilogram (kg)

Question 10

A photon has a wavelength of $$500 	ext{ nm}. $$What is its energy in joules? (Use $$h = 6.63 	imes 10$$^{-34}$$ 	ext{ J} \cdot 	ext{s}$$ and $$c = 3.00 	imes 10^8$ 	ext{ m/s})$$

Accepted Answer

$$E = \frac{hc}{\lambda} = \frac{6.63 	imes 10$$^{-34}$$ 	imes 3.00 	imes 10^8$}{500 	imes 10$$^{-9}$$} = 3.98 	imes 10$$^{-19}$$ 	ext{ J}$$

Question 11

Which transition in the Bohr model would result in the emission of the highest energy photon?

Accepted Answer

From $$n = 2 to$$ $$n = 1$$

Question 12

A student observes a color change in a flame test. Which process is responsible for the observed emission of light?

Accepted Answer

Emission of energy as electrons return to lower energy levels

Question 13

What is the frequency of light with a wavelength of $$600 	ext{ nm}$$? (Use $$c = 3.00 	imes 10^8$ 	ext{ m/s})$$

Accepted Answer

$$
u = \frac{c}{\lambda} = \frac{3.00 	imes 10^8$}{600 	imes 10$$^{-9}$$} = 5.00 	imes 10$$^{14}$$ 	ext{ Hz}$$

Question 14

Which term describes a compound that contains no water molecules?

Accepted Answer

Anhydrous

Question 15

A student calibrates a thermometer before use. What is the purpose of calibration?

Accepted Answer

To ensure the thermometer measures temperature accurately

Question 16

A student records a measurement as $$3.45 	imes 10^4$ g. What is this value in kilograms?

Accepted Answer

$$3.45 	imes 10^4$ 	ext{ g} = 34.5 	ext{ kg}$$

Question 17

Which prefix represents $$10^{-9}$$?

Accepted Answer

Nano

Question 18

An electron transitions from $$n_i = 4 to$$ $$n_f = 2 in a $$hydrogen atom. What is the energy change associated with this transition? (Use $$\Delta E = -2.18 	imes 10$$^{-18}$$ 	ext{ J} (\frac{1}{n_f^2$} - \frac{1}{n_i^2$}))$$

Accepted Answer

$$\Delta E = -2.18 	imes 10$$^{-18}$$ (\frac{1}{2^2$} - \frac{1}{4^2$}) = -2.18 	imes 10$$^{-18}$$ (0.25 - 0.0625) = -2.18 	imes 10$$^{-18}$$ (0.1875) = -4.09 	imes 10$$^{-19}$$ 	ext{ J}$$

Question 19

A student needs to find the volume of a rock by water displacement. The initial water level is 50.0 mL, and after adding the rock, the level rises to 62.5 mL. What is the volume of the rock?

Accepted Answer

$$62.5 	ext{ mL} - 50.0 	ext{ mL} = 12.5 	ext{ mL}$$

Exam #1 Study Guide: Chemistry Math, Lab Techniques, Density, and Atomic Spectra

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