Inorganic Chemistry ACS Exam Study Guide – Latest Questions & A+ Verified Answers

Inorganic Chemistry ACS Exam Study Guide –
Latest Questions & A+ Verified Answers

INORGANIC CHEMISTRY ACS EXAM STUDY GUIDE
300 Multiple Choice Questions with Verified Answers



QUESTION 1

What is the electron configuration of iron (Fe, Z = 26)?

A. [Ar] 3d⁶ 4s²

B. [Ar] 3d⁸

C. [Ar] 3d⁵ 4s²
D. [Kr] 3d⁶ 4s²

E. [Ar] 4s² 3d⁴

CORRECT ANSWER: A. [Ar] 3d⁶ 4s²

RATIONALE: Iron has atomic number 26. After the argon core (18 electrons), the
remaining 8 electrons fill as 3d⁶ 4s², following the Aufbau principle and Hund's rule.



QUESTION 2

Which of the following has the highest electronegativity?
A. Na

B. Mg

C. Al

D. Cl

E. Si

CORRECT ANSWER: D. Cl

RATIONALE: Electronegativity increases across a period and up a group on the
periodic table. Chlorine is the furthest right among the given elements in period 3, giving
it the highest electronegativity (3.16 on the Pauling scale).

,QUESTION 3

Which type of bonding is present in NaCl?

A. Covalent

B. Metallic
C. Polar covalent

D. Ionic

E. Coordinate covalent

CORRECT ANSWER: D. Ionic

RATIONALE: NaCl is formed by the complete transfer of an electron from sodium to
chlorine, creating Na⁺ and Cl⁻ ions held together by electrostatic attraction — the
hallmark of ionic bonding.


QUESTION 4

What is the oxidation state of chromium in K₂Cr₂O₇?

A. +3

B. +4
C. +5

D. +7

E. +6

CORRECT ANSWER: E. +6

RATIONALE: In K₂Cr₂O₇, potassium is +1 and oxygen is -2. Setting up: 2(+1) + 2x
+ 7(-2) = 0 → 2 + 2x - 14 = 0 → x = +6.



QUESTION 5
Which of the following molecules has a trigonal planar geometry?

A. NH₃

B. H₂O

,C. BF₃

D. PCl₅

E. SF₄

CORRECT ANSWER: C. BF₃

RATIONALE: BF₃ has 3 bonding pairs and no lone pairs on the central boron atom,
giving it trigonal planar geometry with 120° bond angles according to VSEPR theory.



QUESTION 6

What is the hybridization of the central atom in SF₆?

A. sp

B. sp²

C. sp³

D. sp³d

E. sp³d²

CORRECT ANSWER: E. sp³d²

RATIONALE: SF₆ has 6 bonding pairs around sulfur with no lone pairs. This
requires 6 hybrid orbitals: one s + three p + two d = sp³d², resulting in an octahedral
geometry.


QUESTION 7

Which of the following is a Lewis acid?

A. NH₃

B. OH⁻

C. H₂O

D. BF₃

E. Cl⁻

CORRECT ANSWER: D. BF₃

, RATIONALE: A Lewis acid is an electron pair acceptor. BF₃ has an empty p orbital
on boron, making it electron-deficient and capable of accepting an electron pair from a
Lewis base.



QUESTION 8

What is the shape of the XeF₄ molecule?

A. Tetrahedral

B. Square planar

C. Seesaw

D. Octahedral

E. T-shaped

CORRECT ANSWER: B. Square planar

RATIONALE: XeF₄ has 4 bonding pairs and 2 lone pairs on xenon (6 electron
domains). The lone pairs occupy axial positions in an octahedral arrangement, leaving
the 4 fluorines in a square planar configuration.


QUESTION 9

Which quantum number describes the shape of an orbital?

A. Principal quantum number (n)

B. Magnetic quantum number (mₗ)

C. Spin quantum number (mₛ)

D. Azimuthal quantum number (l)

E. Nuclear quantum number

CORRECT ANSWER: D. Azimuthal quantum number (l)

RATIONALE: The azimuthal (angular momentum) quantum number l determines
the shape of the orbital: l = 0 (s, spherical), l = 1 (p, dumbbell), l = 2 (d, cloverleaf), etc.


QUESTION 10