Q: A photon has a wavelength of $$4.00 \times 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? $$(h = 6.626 \times 10$$^{-34}$$\ \mathrm{J\cdot s},\ c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$E = \dfrac{hc}{\lambda} = 4.97 \times 10$$^{-19}$$\ \mathrm{J}$$

Question 1

A sample of an unknown metal has a mass of 45.0 g and displaces 16.2 mL of water when submerged. What is the density of the metal, reported with the correct number of significant figures?

Accepted Answer

$$2.78\ \mathrm{g/mL}$$

Question 2

Which of the following correctly expresses the number $$0.0004560 in $$scientific notation with the correct number of significant figures?

Accepted Answer

$$4.560 	imes 10$$^{-4}$$

Question 3

A chemist needs to convert a temperature of $$25.0\ ^\circ\mathrm{C} to $$Kelvin. Which of the following is the correct value and formula used?

Accepted Answer

$$T(K) = T$$(^{\circ}$$\mathrm{C}) + 273.15 = 298.15\ \mathrm{K}$$

Question 4

Which of the following sets of quantum numbers $$(n,\ l,\ m_l) is $$NOT allowed for an electron in an atom?

Accepted Answer

$$(2,\ 2,\ 0)$$

Question 5

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many protons, neutrons, and electrons does it have?

Accepted Answer

17 protons, 18 neutrons, 17 electrons

Question 6

Which of the following correctly ranks electromagnetic radiation from lowest to highest frequency?

Accepted Answer

Radio waves \u003c Infrared \u003c Visible \u003c Ultraviolet \u003c X-rays

Question 7

A photon has a wavelength of $$4.00 	imes 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? $$(h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s},\ c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$E = \dfrac{hc}{\lambda} = 4.97 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 8

Which of the following best explains why the atomic radius decreases across a period from left to right?

Accepted Answer

Increasing nuclear charge pulls electrons closer to the nucleus, reducing atomic size.

Question 9

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F}^-$$

Question 10

A sample contains two isotopes of magnesium: $$^{24}\mathrm{Mg} (78.99$$% abundance, mass = 23.985 amu) and $$^{26}\mathrm{Mg} (21.01$$% abundance, mass = 25.983 amu). What is the average atomic mass of magnesium?

Accepted Answer

$$24.31\ \mathrm{amu}$$

Question 11

Which of the following electron configurations represents a violation of the Pauli Exclusion Principle?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^7$$

Question 12

Which of the following best describes Hund’s Rule?

Accepted Answer

Electrons fill degenerate orbitals singly before pairing.

Question 13

A hydrogen atom makes a transition from $$n=4 to$$ $$n=2. $$What is the wavelength of the emitted photon? $$(R_H = 1.0974 	imes 10^7$\ \mathrm{m}^{-1})$$

Accepted Answer

$$\lambda = \dfrac{1}{R_H\left(\dfrac{1}{2^2$} - \dfrac{1}{4^2$}\right)} = 486\ \mathrm{nm}$$

Question 14

Which of the following best describes the Heisenberg Uncertainty Principle?

Accepted Answer

$$\Delta x \Delta p \geq \dfrac{h}{4\pi}$$

Question 15

Which of the following best explains why sodium ($$\mathrm{Na}) $$forms a $$+1$$ ion?

Accepted Answer

It loses one electron to achieve a noble gas electron configuration.

Question 16

Which of the following compounds is named correctly according to IUPAC nomenclature rules?

Accepted Answer

Iron(III) chloride for $$\mathrm{FeCl}_3$$

Question 17

Which of the following best describes the difference between core and valence electrons?

Accepted Answer

Valence electrons are in the outermost shell and participate in bonding, while core electrons are in inner shells and do not.

Question 18

Which of the following best explains why $$\mathrm{O}_2 is $$paramagnetic?

Accepted Answer

It has unpaired electrons in its molecular orbitals.

Question 19

A $$2.0\ \mathrm{g}$$ particle is moving at $$3.0\ \mathrm{m/s}. $$What is its de Broglie wavelength? $$(h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s})$$

Accepted Answer

$$\lambda = \dfrac{h}{mv} = 1.1 	imes 10$$^{-34}$$\ \mathrm{m}$$

General Chemistry I: Midterm 1 Study Guide (Chapters 1, 2, 3.1-3.7, 8, 9)

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