Q: How many oxygen atoms are in $$2.50 g of$$ $$SiO_2$$? ($$M_{$$SiO_2$$} = 60.08 g/$$mol, $$N_A = 6.022 \times 10$$^{23}$$ mol$$^{-1}$$)

$$5.01 \times 10$$^{22}$$ atoms

Q: How many photons are contained in a flash of green light ($$525 nm) $$that contains $$189 kJ of $$energy? ($$h = 6.626 \times 10$$^{-34}$$ J·s, c = 3.00$$ \times $$10^8 m/s)$$

$$5.67 \times 10$$^{23}$$ photons

Q: What is the energy of light associated with a transition from $$n=3 to$$ $$n=8 in a $$hydrogen atom? Does this represent absorption or emission of a photon? ($$E = -2.18 \times 10$$^{-18}$$ (\frac{1}{n_f^2$} - \frac{1}{n_i^2$}) J)$$

$$2.08 \times 10$$^{-19}$$ J, absorption

Question 1

Read the length of the metal bar with the correct number of significant figures based on the image provided.

Accepted Answer

15.0 cm

Question 2

What answer should be reported, with the correct number of significant figures, for the following calculation? $$\$$ \frac{249.362 + 41}{63.498} \$

Accepted Answer

4.57

Question 3

Convert $$5\ \mu m ($$micrometers) to nanometers.

Accepted Answer

$$5 	imes 10^3$ nm

Question 4

The recommended adult dose of Elixophyllin is $$6.00\ mg/kg of $$body mass. Calculate the dose in milligrams for a $$112-lb $$person. (1 kg = 2.20 lb)

Accepted Answer

305 mg

Question 5

Milk is best classified as which type of mixture?

Accepted Answer

Heterogeneous

Question 6

Determine the number of protons, neutrons, and electrons in the isotope $$^{25}_{12}X.$$

Accepted Answer

p$$^+ = 12$$, n$$^0 = 13$$, e$$^- = 12$$

Question 7

Calculate the atomic mass of element X, if it has two naturally occurring isotopes with the following masses and natural abundances: $$X-107$$: $$106.90509$$ amu (51.84%), $$X-109$$: $$108.90476$$ amu (48.46%).

Accepted Answer

107.79 amu

Question 8

Silver has an atomic mass of $$107.868$$ amu. The Ag-109 isotope ($$108.905$$ amu) is $$48.161\%. $$What is the amu of the other isotope?

Accepted Answer

106.905 amu

Question 9

How many oxygen atoms are in $$2.50 g of$$ $$SiO_2$$? ($$M_{$$SiO_2$$} = 60.08 g/$$mol, $$N_A = 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

$$5.01 	imes 10$$^{22}$$ atoms

Question 10

Which of the following types of visible light has the lowest frequency?

Accepted Answer

Orange

Question 11

Calculate the frequency of light emitted by a hydrogen atom with a wavelength of $$384.2 nm$$. ($$c = 3.00 	imes 10^8$ m/s)

Accepted Answer

$$7.81 	imes 10$$^{14}$$ Hz

Question 12

How many photons are contained in a flash of green light ($$525 nm) $$that contains $$189 kJ of $$energy? ($$h = 6.626 	imes 10$$^{-34}$$ J·s, c = 3.00$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$5.67 	imes 10$$^{23}$$ photons

Question 13

What is the energy of light associated with a transition from $$n=3 to$$ $$n=8 in a $$hydrogen atom? Does this represent absorption or emission of a photon? ($$E = -2.18 	imes 10$$^{-18}$$ (\frac{1}{n_f^2$} - \frac{1}{n_i^2$}) J)$$

Accepted Answer

$$2.08 	imes 10$$^{-19}$$ J, absorption

General Chemistry Study Guide: Measurement and Significant Figures

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