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Quiz about Chemistry Questions for the DieHard Chem Fan

Chemistry Questions for the Die-Hard Chem Fan Quiz

The questions I've put here are competition-level ones and are, at least, at High School level. Some questions require computation and serious analytical thinking. Recommended for die-hard chemistry enthusiasts.

A multiple-choice quiz by metamorphmagus. Estimated time: 7 mins.

Author
metamorphmagus

Time
7 mins

Type
Multiple Choice

Quiz #
294,530

Updated
Dec 03 21

# Qns
10

Difficulty
Difficult

Avg Score
5 / 10

Plays
810

One at a Time - Single Page - Timed Game

Question 1 of 10

1. The atomic masses in the periodic table are not integral numbers. For example, carbon is listed as 12.011 amu (atomic mass unit) instead of 12.000 amu. Why? Hint

Atomic masses are measured in real samples that are always contaminated with other elements.

There is a theoretical uncertainty in the masses of atoms.

Atoms gain and lose electrons easily and that changes their masses significantly.

Atomic masses listed in the periodic table are weighted averages of isotopic masses.

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Question 2 of 10

2. Screening by core electrons in atoms is _______. Hint

responsible for a general decrease in atomic radius going down a group

less efficient than that by valence electrons

more efficient than that by valence electrons

essentially identical to that by valence electrons

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Question 3 of 10

3. According to the Valence Shell Electron Pair Repulsion theory, if there are 5 pairs of electrons in the valence shell of an atom, they will be arranged in a(n) _____ geometry. Hint

octahedral

trigonal planar

tetrahedral

trigonal bipyramidal

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Question 4 of 10

4. What is the mass in grams of 10.0 million H2O molecules? Hint

1.800 x 10^8

2.990 x 10^-16

1.661 x 10^-17

2.990 x 10^-23

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Question 5 of 10

5. Which of the following is a valid set of quantum numbers? Hint

n=3, l=2, ml=-3, ms=+1/2

all of the above

n=1, l=0, ml=1, ms=+1/2

n=4, l=0, ml=0, ms=-1/2

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Question 6 of 10

6. Phenol red has an indicator pH range of 6.8 to 8.4. Its acid color is yellow and basic color is red. In 0.10 M NaOH, this indicator will exhibit what color? Hint

cannot be determined

red

orange

yellow

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Question 7 of 10

7. Determine the volume (in liters) occupied by 8.0 g oxygen at STP (MW of O2 = 32 g/mol)

Answer: (answer in two significant figures, omit the unit of measurement)

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Question 8 of 10

8. What do you call gases that do not conform to the ideal gas laws?

Answer: (Two Words, second word, "gases.")

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Question 9 of 10

9. Which of the following terms is used to describe the amount of heat present in a substance? Hint

enthalpy

heat capacity

specific heat

entropy

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Question 10 of 10

10. How many grams of phosphoric acid (98 g/mol) are in 175 mL of a 3.5 M solution of phosphoric acid?

Answer: (two significant figures)

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Quiz Answer Key and Fun Facts

1. The atomic masses in the periodic table are not integral numbers. For example, carbon is listed as 12.011 amu (atomic mass unit) instead of 12.000 amu. Why?

Answer: Atomic masses listed in the periodic table are weighted averages of isotopic masses.

The atomic masses listed on the periodic table are, actually, average atomic masses. The average atomic mass is the summation of the products of an element's isotopic masses and its relative abundance (in percent). For example, carbon has two common isotopes: C-12 and C-13. C-12 is 98.9% abundant and has a mass of 12.000 amu, whereas C-13 is 1.1% abundant and has a mass of 13.0033 amu. Computing for carbon's average atomic mass: (12.0000 * 0.989) + (13.0033 * 0.011) = 12.011 amu.

2. Screening by core electrons in atoms is _______.

Answer: more efficient than that by valence electrons

Core electrons, unlike valence electrons, do not participate in bonding. It is more efficient to screen atoms by their core electrons because the amount of core electrons do not get affected by bonding (not in the case of valence electrons).

3. According to the Valence Shell Electron Pair Repulsion theory, if there are 5 pairs of electrons in the valence shell of an atom, they will be arranged in a(n) _____ geometry.

Answer: trigonal bipyramidal

O

octahedral : 6 pairs of electrons
tetrahedral : 4 pairs of electrons
trigonal planar : 3 pairs of electrons.

4. What is the mass in grams of 10.0 million H2O molecules?

Answer: 2.990 x 10^-16

Determine how many moles of water is present in the 10.0 million molecules [10,000,000 molecules / (6.02 x 10^23 molecules per mole)]. Multiply this quantity (1.661 x 10^-17 mole) to the molecular weight of water (18.00 g/mole) and you'll get 2.990 x 10^-16 g.

5. Which of the following is a valid set of quantum numbers?

Answer: n=4, l=0, ml=0, ms=-1/2

N

n=3, l=2, ml=-3, ms=+1/2
Invalid because the ml values for d (l=2) orbitals are -2, -1, 0, 1, and 2.

n=1, l=0, ml=1, ms=+1/2
Invalid because ml cannot be 1 if l=0. l=0 specifies an s orbital and the ml value of an s orbital is 0.

n=4, l=0, ml=0, ms=-1/2
Valid. Describes an electron in the s orbital of the 4th energy level.

6. Phenol red has an indicator pH range of 6.8 to 8.4. Its acid color is yellow and basic color is red. In 0.10 M NaOH, this indicator will exhibit what color?

Answer: red

0.10 M NaOH has a pH of 13. This value is higher than the upper limit of the pH range. Therefore, the red color will be exhibited by the indicator.

7. Determine the volume (in liters) occupied by 8.0 g oxygen at STP (MW of O2 = 32 g/mol)

Answer: 5.6

Using the Ideal Gas Equation, PV=nRT, V=nRT/P. At standard temperature and pressure (STP), T=273 K and P = 1.0 atm.

8. What do you call gases that do not conform to the ideal gas laws?

Answer: real gases

Real gas effects refers to an assumption base where the following are taken into account:

* Compressibility effects
* Variable heat capacity
* Van der Waals forces
* Non-equilibrium thermodynamic effects
* Issues with molecular dissociation and elementary reactions with variable
composition.

9. Which of the following terms is used to describe the amount of heat present in a substance?

Answer: enthalpy

Enthalpy comes from the Greek word, "enthalpein," which means, "to warm in." The symbol for enthalpy is "H."

10. How many grams of phosphoric acid (98 g/mol) are in 175 mL of a 3.5 M solution of phosphoric acid?

Answer: 60

(1)Molarity = no. of moles solute/volume, in liters, of solution

(2) no of moles = wt / molecular wt

Plugging in eq (2) in eq (1):

Molarity = wt/(Molecular wt X Volume in liters)

Solving for the value of wt:

wt = Molarity X molecular wt X Volume, in liters

= 3.75 mol/L X 98 g/mol X 0.175 L
= 60.025
= 60 g

Source: Author metamorphmagus

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