Question 1

Which of the following statements best explains why electromagnetic radiation with a shorter wavelength has higher energy?

Accepted Answer

Because frequency increases as wavelength decreases, and energy is proportional to frequency: $$E = h 
u$$

Question 2

A sample contains $$7.31 	imes 10$$^{15}$$ molecules of NO_2$. How many moles of NO_2$ are present?

Accepted Answer

$$1.21 	imes 10$$^{-8}$$ mol

Question 3

Which of the following elements has the highest ionization energy?

Accepted Answer

chlorine

Question 4

Calculate the wavelength, in meters, of electromagnetic radiation that has a frequency of $$4.51 	imes 10$$^{14}$$ Hz. Use c = 2.99$$ 	imes $$10^8 m/s.$$

Accepted Answer

$$6.63 	imes 10$$^{-7}$$ m

Question 5

Which of the following is the correct noble gas electron configuration for an atom of cobalt?

Accepted Answer

$$[Ar] 3d^7$ 4s^2$

Question 6

A compound has a molar mass of 60.0 g/mol and an empirical formula of $$CH_2O. $$What is the molecular formula of the compound?

Accepted Answer

$$C_2H_4O_2$$

Question 7

Determine the number of moles of carbon present in a $$0.345$$ mole sample of acetic acid, $$HC_2H_3O_2.$$

Accepted Answer

$$0.690$$ mol C

Question 8

Which of the following is a reactant in the chemical reaction: $$Zn (s) + 2HCl (aq) \rightarrow H_2$ (g) + $$ZnCl_2$$ (aq)$$?

Accepted Answer

hydrochloric acid

Question 9

Classify the following reaction: $$HNO_3 (aq) + $$NaOH (aq) \rightarrow H_2O (l) + $$NaNO_3 (aq$$)$$

Accepted Answer

double replacement

Question 10

Which of the following best describes oxidation?

Accepted Answer

a loss of electrons

Question 11

How many orbitals are there in the $$n = 4$$ principal shell?

Accepted Answer

16

Question 12

What is the total number of electrons possible in a $$3p$$ subshell?

Accepted Answer

6

Question 13

Calculate the mass, in grams, of a $$1.53$$ mole sample of lithium. (Atomic mass of Li = $$6.94 g/$$mol)

Accepted Answer

$$10.6 g$$

Question 14

Which of the following atoms has the largest atomic radius?

Accepted Answer

magnesium

Question 15

Indicate the physical state of potassium in the following reaction: $$K(s) + H_2O(l) \rightarrow H_2$(g)$$

Accepted Answer

solid

Question 16

A quantum packet of energy that has both particle and wave properties is called:

Accepted Answer

a photon

Question 17

Calculate the molar mass of $$Ba(NO_3$)_2.$$

Accepted Answer

$$261.3 g/$$mol

Question 18

Determine the percentage composition, by mass, of nitrogen in $$N_2O.$$

Accepted Answer

$$63.65\% N$$

Question 19

Consider the following: $$Fe^{3+} (aq) + e$$^- \rightarrow $$Fe^{2+} (aq$$)$$. The reaction above represents:

Accepted Answer

reduction

Question 20

Which of the following best describes the role of $$Na in $$the reaction $$2Na (s) + Cl_2$ (g) \rightarrow 2NaCl (s)$$?

Accepted Answer

It is oxidized, losing electrons to form $$Na^+$$ ions.

Introduction to Chemistry: Key Concepts and Practice Questions

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