Week 1 Balancing, Oxid, Polarity, etc.

What is the oxidation number of the chlorine atoms in Cl₂?

• 2

• 17

• 35.45

• -1

• 0

Answer explanation

Elements in their atomic state have an oxidation number of 0 (Cl is one of the seven diatomic elements). Additionally, there is no other value for each of the chlorine atoms that could add up to 0.

Rank these single bonds from least polar to most polar:

C-O, H-F, P-S, Br-Br.

• H-F < C-O < P-S < Br-Br

• H-F < P-S < C-O < Br-Br

• Br-Br < H-F < P-S < C-O

• Br-Br < C-O < P-S < H-F

• Br-Br < P-S < C-O < H-F

Answer explanation

H = 2.1

F = 4.0

O = 3.5

N = 3.0

C = 2.5

B = 2.0

Cl = 3.16

S = 2.58

P = 2.19

Br = 3.0

I = 2.66

Tags

NGSS.HS-PS1-3

When this equation is balanced, what is the sum of the coefficients?

Au³⁺(aq) + I^‒(aq) → Au(s) + I₂(s)

• 5

• 2

• 13

• 9

• 7

Tags

NGSS.HS-PS1-7

Arrange these compounds in order of increasing melting point:

BaS, KCl, LiF, NaCl, CaO

• CaO < BaS < LiF < KCl < NaCl

• NaCl < KCl < LiF < BaS < CaO

• LiF < NaCl < KCl < CaO < BaS

• BaS < CaO < KCl < NaCl < LiF

• KCl < NaCl < LiF < BaS < CaO

Answer explanation

First, consider the charge (larger is stronger attraction), and then consider the size (smaller is stronger attraction).

What is the sum of the coefficients in the balanced redox reaction when Au³⁺ and I^– react in solution to form elemental products?

• 5

• 6

• 8

• 9

• 13

In which of these species is the sulfur atom in the highest oxidation state?

• H₂S

• SO₄^2-

• S^2-

• SO₂

• SF₆

Answer explanation

Draw Lewis structures, give electrons to the most electronegative atom.

Valence electrons - # of electrons owned = oxidation number

When the following equation is balanced using the smallest whole number coefficients, what is the sum of the coefficients?

H₃PO₄ (aq) + Ba(OH)₂(s) → Ba₃(PO₄)₂(s) + H₂O(ℓ)

• 8

• 10

• 12

• 14

• 16

Which of these compounds has the highest melting point?

• AlCl₃

• SiCl₄

• PCl₃

• SCl₂

• Cl₂

Answer explanation

This question is about melting points of various substances. Ionic compounds have higher melting points than covalent compounds. AlCl₃ is the only ionic compound given.

Which of the compounds below contains an element that is in a +6 oxidation state?

• Al₂O₃

• NaNO₃

• KMnO₄

• H₃PO₄

• H₂SO₄