Q: A patient is given a radioactive isotope that emits light with a wavelength of $$5.00 \times 10$$^{-7}$$\ \mathrm{m}. $$What is the energy of a single photon emitted? ($$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J\cdot s}$$, $$c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$3.98 \times 10$$^{-19}$$\ \mathrm{J}$$

Question 1

Which of the following statements best describes the concept of enthalpy ($$\Delta H) in a $$chemical reaction?

Accepted Answer

It is the heat absorbed or released at constant pressure.

Question 2

A sample of gas absorbs 150 J of heat and does 40 J of work on the surroundings. What is the change in internal energy ($$\Delta U) of $$the system?

Accepted Answer

$$\Delta U = 110\ \mathrm{J}$$

Question 3

Which of the following best illustrates Hess’s Law?

Accepted Answer

The enthalpy change of a reaction is independent of the pathway between initial and final states.

Question 4

Which of the following equations correctly represents the relationship between the speed of light ($$c$$), wavelength ($$\lambda$$), and frequency ($$
u$$)?

Accepted Answer

$$c = \lambda 
u$$

Question 5

The emission spectrum of hydrogen consists of discrete lines because:

Accepted Answer

Electrons can only occupy specific energy levels in the atom.

Question 6

Which set of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 7

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 8

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 9

Which of the following best describes a coordinate covalent bond?

Accepted Answer

A bond in which both electrons are donated by the same atom.

Question 10

Which of the following molecules violates the octet rule by having fewer than eight electrons around the central atom?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 11

What is the formal charge on the central atom in the Lewis structure of $$\mathrm{NO_3$^-} ($$nitrate ion)?

Accepted Answer

0

Question 12

Which of the following molecules exhibits resonance?

Accepted Answer

$$\mathrm{O_3$}$$

Question 13

According to VSEPR theory, what is the molecular geometry of $$\mathrm{SF_4$}$$?

Accepted Answer

Seesaw

Question 14

Which of the following statements about hybridization is correct?

Accepted Answer

An atom with three electron groups around it will be $$sp^2$$ hybridized.

Question 15

Which of the following best explains why $$\mathrm{H_2O} is a $$polar molecule?

Accepted Answer

It has a bent molecular geometry and polar O–H bonds.

Question 16

Which of the following is the correct electron configuration for a ground-state phosphorus atom ($$Z=15$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^3$$

Question 17

A patient is given a radioactive isotope that emits light with a wavelength of $$5.00 	imes 10$$^{-7}$$\ \mathrm{m}. $$What is the energy of a single photon emitted? ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$3.98 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 18

Which of the following statements about multiple covalent bonds is correct?

Accepted Answer

A double bond consists of one sigma ($$\sigma) $$and one pi ($$\pi) $$bond.

Question 19

Which of the following best describes the relationship between electronegativity and bond polarity?

Accepted Answer

The greater the difference in electronegativity, the more polar the bond.

Question 20

Which hybridization scheme is used by the central atom in $$\mathrm{SF_6$}$$?

Accepted Answer

$$sp^3d^2$

Exam #3 Study Guide: Thermochemistry, Electronic Structure, and Chemical Bonding

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