Chemistry Exam 1 Practice

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Questions and Answers

What is the value of Avogadro’s number?

3.00 x 10^8

1.6726 x 10^-27

6.022 x 10^23 (correct)

9.1094 x 10^-31

Which constant represents the speed of light?

-1.60218 x 10^-19 C

1.097 x 10^7 1/m

3.00 x 10^8 m s^-1 (correct)

6.626 x 10^-34 J s

How does the mass of a neutron compare to that of a proton?

They are identical in mass.

The mass of a neutron is irrelevant.

The neutron is heavier than the proton. (correct)

The neutron is slightly lighter than the proton.

What is the relationship between Kelvin and Celsius at absolute zero?

0 K corresponds with -273.15°C. Signup and view all the answers

What is the value of the gas constant (R)?

0.08206 L atm mol^-1 K^-1 Signup and view all the answers

What is the molecular geometry of the astatine atom in Br4At?

Tetrahedral Signup and view all the answers

What is the electron geometry around the nitrogen atom if it shows trigonal planar geometry?

Trigonal planar Signup and view all the answers

How many sigma bonds are present in the Lewis structure being referenced?

3 Signup and view all the answers

Which of the following statements is true regarding the polarity of the indicated molecules?

Only molecule A is nonpolar. Signup and view all the answers

What is the molecular formula for the ionic compound formed by calcium and the arsenate ion?

Ca3(AsO4)2 Signup and view all the answers

What type of intermolecular force would be present between two identical molecules?

London dispersion forces Signup and view all the answers

Is the arsenate ion polar?

Yes, it is polar Signup and view all the answers

What formal charge would be indicated for a neutral atom in a Lewis structure?

0 Signup and view all the answers

Which bond is likely to be the longest bond on average?

C-C bond Signup and view all the answers

What is the electron geometry around the nitrogen atom?

Tetrahedral Signup and view all the answers

What is the expected bond angle in a tetrahedral molecular geometry?

109.5 degrees Signup and view all the answers

What is the hybridization state of the carbon indicated with an arrow?

sp2 Signup and view all the answers

When considering molecular geometry, what would the bond angles around an atom with trigonal planar geometry generally be?

120 degrees Signup and view all the answers

Which angle is deduced to be larger, the C-O-C angle or the H-P-H angle?

H-P-H Signup and view all the answers

Which of the following correctly describes the Lewis structure for SNCl2+?

S has one lone pair Signup and view all the answers

What is necessary for full credit when solving math problems on the exam?

Work must be shown along with the final answer. Signup and view all the answers

Which items must be stored properly during the exam?

Electronic devices, except for a calculator. Signup and view all the answers

How much time is allocated for completion of the exam?

50 minutes Signup and view all the answers

What is required when reporting answers on the exam?

Both correct units and number of significant digits must be included. Signup and view all the answers

What must students do if they want to ask a question during the exam?

Only ask for clarification. Signup and view all the answers

Where should scratch work or additional calculations be recorded?

On the back of the exam paper only. Signup and view all the answers

What must students do to affirm their adherence to the University Honor Code?

Sign the honor pledge on the exam sheet. Signup and view all the answers

What happens to an answer without accompanying work, regardless of its correctness?

It will be awarded zero points. Signup and view all the answers

What is the relationship between energy, frequency, and Planck's constant in photon interactions?

E = hν Signup and view all the answers

What is the correct equation to calculate the molar mass of a compound given its empirical formula mass?

molar mass = empirical formula mass × n Signup and view all the answers

Which formula represents the relationship between pressure, volume, and temperature in a gas?

PV = nRT Signup and view all the answers

What is the empirical formula's molar mass if an empirical formula has a mass of 12 g/mol, and n equals 2?

24 g/mol Signup and view all the answers

What value would indicate a pure covalent bond based on electronegativity difference?

0 Signup and view all the answers

Which equation calculates the kinetic energy of an electron?

KE = 1/2 mv² Signup and view all the answers

How is the formal charge of a molecule calculated?

Formal charge = Ve− − (Be− + LPe−) Signup and view all the answers

What is the correct relationship for calculating the equilibrium constant from the concentrations of reactants and products?

K = [products]/[reactants] Signup and view all the answers

What is the formula used to determine the fraction of ions in a solution i.e., the percentage ionization?

%ion = ([H₃O⁺]/[HA]) × 100 Signup and view all the answers

What is the definition of the concept of effective nuclear charge (Zeff)?

Zeff = Z - S Signup and view all the answers

Study Notes

Exam 1 Practice

The average score on the exam was 72%
Students should treat this practice exam like a real exam and time themselves for 50 minutes
Only a calculator and a periodic table and formula sheet are allowed
Use pencil, write legibly, and show all work and calculations
Answers without accompanying work receive zero points
Report answers with the correct units and significant figures
Clarification questions are allowed, but no help with questions
Any corrections to the exam will be written on the board and announced
Scratch work should be done on the back page and clearly labeled
The honor code requires students to acknowledge that they have not given or received any assistance on the exam

Molecular Formulas and Names

Na2Se: Sodium Selenide
Nickel (II) Carbonate: NiCO3
Dinitrogen Trioxide: N2O3
(NH4)3P: Ammonium Phosphide
Pb(CrO4)2: Lead (II) Chromate

Calcium Arsenate

The formula for Calcium Arsenate is Ca3(AsO4)2
The arsenate ion is polar
The most stable resonance structure for the arsenate ion is the one with the negative charges on the oxygen atoms that are not double bonded to the phosphorus

Molecular Geometry

The molecular geometry around phosphorus is tetrahedral
The C-O-C angle is larger than the H-P-H angle
The electron geometry around the nitrogen is tetrahedral
The N-H bond is the longest bond on average
The hybridization around the carbon marked with an arrow is sp3
The N - H bond is formed by the overlap of an sp3 and an s orbital
The C - C bond is formed by the overlap of an sp3 and an sp3 orbital
Four unhybridized p orbitals are used for bonding in this molecule

SNCl2+

The Lewis structure for SNCl2+ has 26 valence electrons
There is a formal charge of +1 on the sulfur atom and a formal charge of -1 on one chlorine atom

Br 4At

The VSEPR-3D model shows the bromine atoms in a square planar arrangement around the astatine
The electron geometry around the astatine is square planar
The molecular geometry around the astatine is square planar
The bond angles around astatine are 90 degrees
The molecule is nonpolar

Phosphorus and Chlorine Molecule

There is a formal charge of +1 on the phosphorus atom and a formal charge of -1 on one chlorine atom
The phosphorus atom has a tetrahedral molecular geometry
The molecule is polar

Intermolecular Forces

Hydrogen bonding and dipole-dipole forces are present between molecules with hydrogen bonding (like water)
Dipole-dipole forces are present between polar molecules
London dispersion forces are present between all molecules

Polarity

Both Molecule A and Molecule B are polar

Nitrogen Molecule

There are 5 sigma bonds in the given structure
There are 2 pi bonds in the given structure
The electron geometry around nitrogen is trigonal planar
The resonance structure that accounts for the trigonal planar geometry around the nitrogen atom shows a double bond between the nitrogen and one of the oxygens, a single bond between the nitrogen and the other oxygen, and a lone pair on the positively charged nitrogen

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Description

Prepare for your Chemistry Exam 1 with this practice quiz that mimics the exam conditions. Covering key topics such as molecular formulas and naming compounds, this quiz is designed to enhance your understanding and performance. Remember to time yourself and show all work for complete credit.