Free NYSTCE Chemistry Questions and Answers — Questions and Answers

Question 1: In general, how do atomic masses vary across the periodic table of elements?

They increase from right to left and top to bottom.
They increase from right to left and bottom to top.
They increase from left to right and top to bottom. (Correct answer)
They increase from left to right and bottom to top.

Correct answer: They increase from left to right and top to bottom.

The periodic table is fundamentally organized by increasing atomic number, which generally correlates with increasing atomic mass. As you move from left to right across a period, the number of protons and neutrons increases, and similarly, moving down a group adds more electron shells and mass. This consistent trend results in atomic masses generally increasing from left to right and top to bottom.

Question 2: How many moles of carbon-12 are there in 6 grams of carbon-12?

0.5 mole (Correct answer)
3.01 ×1023 moles
2.0 moles
6.02 ×1023 moles

Correct answer: 0.5 mole

One mole of any element is defined as its atomic mass expressed in grams. For carbon-12, the atomic mass is 12 atomic mass units (amu), meaning one mole of carbon-12 weighs 12 grams. Therefore, 6 grams of carbon-12 represents exactly half of a mole (6g / 12g/mol = 0.5 mol).

Question 3: Which of these atoms has the greatest atomic radius?

magnesium (Mg)
barium (Ba) (Correct answer)
iodine (I)
chlorine (Cl)

Correct answer: barium (Ba)

Atomic radius generally increases as you move down a group and decreases as you move across a period from left to right on the periodic table. Barium (Ba) is located in Group 2, Period 6, placing it significantly lower and further left than magnesium (Group 2, Period 3), iodine (Group 17, Period 5), and chlorine (Group 17, Period 3). Its position indicates more electron shells and weaker attraction from the nucleus to the outermost electrons, resulting in the largest atomic radius among the choices.

Question 4: Why is cobalt (Co) listed before nickel (Ni) on the periodic table of elements, despite having a higher average atomic mass?

Cobalt has a lower density.
Cobalt was discovered first.
Nickel has one more proton. (Correct answer)
Nickel has fewer electrons.

Correct answer: Nickel has one more proton.

The periodic table is primarily ordered by increasing atomic number, which represents the number of protons in an atom's nucleus. Cobalt (Co) has an atomic number of 27, while Nickel (Ni) has an atomic number of 28. Even though cobalt's average atomic mass is slightly higher due to the relative abundance of its isotopes, its lower atomic number dictates its placement before nickel on the periodic table.

Question 5: In theory, as an ideal gas cools in a closed container, the pressure inside gradually decreases until it approaches that of a vacuum. What temperature should this happen at?

0 K (Correct answer)
−273 K
0 °C
−460 °C

Correct answer: 0 K

This scenario describes the theoretical concept of absolute zero, which is 0 Kelvin (K). At this temperature, all molecular motion of an ideal gas would cease, meaning the particles would exert no force on the container walls. Consequently, the pressure inside the container would drop to zero, approaching that of a vacuum.

Question 6: Which of the following accurately describes the rate of this chemical reaction?

a decrease in HCl and Cl2 with time
an increase in H2 and Cl2 with time
an increase in the concentration of HCl and H2 with time
an increase in the concentration of HCl with time (Correct answer)

Correct answer: an increase in the concentration of HCl with time

The rate of a chemical reaction is typically measured by observing how the concentration of reactants decreases or how the concentration of products increases over time. If HCl is a product of the reaction, its concentration will naturally increase as the reaction progresses. Therefore, an increase in the concentration of HCl with time accurately describes its formation rate.

Question 7: When a cold tire is inflated to a specific pressure and then heated by road friction, the pressure increases. <br>This occurs because of

air molecules speed up and collide with the tire walls more often. (Correct answer)
rubber in the tire reacts with oxygen in the atmosphere.
air molecules hit the walls of the tire less frequently.
air molecules diffuse rapidly through the walls of the tire.

Correct answer: air molecules speed up and collide with the tire walls more often.

According to the kinetic theory of gases, increasing the temperature of a gas causes its molecules to gain kinetic energy and move faster. These faster-moving air molecules collide with the tire walls more frequently and with greater force. This increased frequency and intensity of collisions directly results in a higher pressure inside the tire.

Question 8: Which substance is composed of numerous monomers joined in long chains?

protein (Correct answer)
ethanol
propane
salt

Correct answer: protein

Proteins are large biological macromolecules (polymers) that are constructed from smaller, repeating units called amino acids (monomers). These amino acids link together in long chains via peptide bonds, which then fold into complex three-dimensional structures. This characteristic 'monomers joined in long chains' is a defining feature of proteins and other polymers.

Question 9: Which statement best describes the density of the nucleus of an atom?

The nucleus occupies most of the atom’s volume and contains most of its mass
The nucleus occupies most of the atom’s volume but contains little of its mass.
The nucleus occupies very little of the atom’s volume but contains most of its mass. (Correct answer)
The nucleus occupies very little of the atom’s volume and contains little of its mass.

Correct answer: The nucleus occupies very little of the atom’s volume but contains most of its mass.

The nucleus of an atom is incredibly dense because it contains almost all of the atom's mass (protons and neutrons) concentrated in a very small volume. The electrons, which contribute negligible mass, occupy a much larger volume around the nucleus. This makes the nucleus extremely compact and accounts for the vast majority of the atom's mass despite its tiny size.

Question 10: Which action will cause the above response to shift to the right?

heating the equilibrium mixture
adding water to the system
increasing the system’s pressure (Correct answer)
decreasing the oxygen concentration

Correct answer: increasing the system’s pressure

According to Le Chatelier's Principle, increasing the pressure on a gaseous equilibrium system will cause the reaction to shift towards the side with fewer moles of gas to alleviate the stress. If the right side of the reaction has fewer moles of gas compared to the left, increasing the pressure will favor the formation of products, thus shifting the equilibrium to the right.

Question 11: What is the equivalent in degrees Celsius of 423 kelvin?

–223 °C
–23 °C
696 °C
150 °C (Correct answer)

Correct answer: 150 °C

To convert a temperature from Kelvin to Celsius, you subtract 273.15 from the Kelvin value. Therefore, 423 K - 273.15 = 149.85 °C. Rounding this to the nearest whole number gives 150 °C, which is the equivalent temperature in degrees Celsius.

Question 12: The above model of ideal gases is useful because:

gives precise explanations for non-ideal gas behavior.
shows a linear relation between gas pressure and volume.
predicts the behavior of other phases of matter.
accurately approximates the properties of most gas molecules. (Correct answer)

Correct answer: accurately approximates the properties of most gas molecules.

The ideal gas model simplifies gas behavior by assuming particles have no volume and no intermolecular forces. While no real gas is perfectly ideal, this model provides an excellent approximation for the behavior of most gases under conditions of high temperature and low pressure. This makes it a highly useful tool for predicting and understanding gas properties in many practical applications.

Question 13: "Which of the following procedures will decrease the rate of reaction if the reaction below occurs in a sealed reaction chamber?<br> 2CO + O2 ---> 2CO2"

removing the CO2 as it is formed
adding more CO to the reaction chamber
increasing the volume inside the reaction chamber (Correct answer)
raising the temperature of the reaction chamber

Correct answer: increasing the volume inside the reaction chamber

Increasing the volume of the reaction chamber for a gaseous reaction reduces the concentration of the reactant molecules (CO and O2). A lower concentration means that reactant molecules will collide less frequently. Since reaction rate is dependent on the frequency of effective collisions, a decrease in collision frequency will lead to a slower reaction rate.

Question 14: Hydrogen peroxide naturally degrades over time into H2O and O2. MnO2 (manganese dioxide) can be used to decrease the activation energy required for this reaction, thereby accelerating its rate.<br> What kind of material is MnO2?

a catalyst (Correct answer)
an inhibitor
an enhancer
a reactant

Correct answer: a catalyst

A catalyst is a substance that speeds up the rate of a chemical reaction without being consumed in the process. It achieves this by lowering the activation energy required for the reaction to occur, providing an alternative reaction pathway. MnO2 fits this definition perfectly by accelerating the decomposition of hydrogen peroxide without being used up itself.

Question 15: Which of the following elements shares silicon's Lewis dot structure?

aluminum (Al)
gallium (Ga)
germanium (Ge) (Correct answer)
arsenic (As)

Correct answer: germanium (Ge)

Elements in the same group (vertical column) of the periodic table have the same number of valence electrons, which dictates their Lewis dot structure. Silicon (Si) is in Group 14 and has 4 valence electrons. Germanium (Ge) is also in Group 14, directly below silicon, and therefore shares the same number of valence electrons and an identical Lewis dot structure.

Question 16: For a hypothesis to reach the level of a theory it must be.

obviously accepted by most people.
a fully functional experiment.
in alignment with past theories.
repeatedly confirmed by experimentation. (Correct answer)

Correct answer: repeatedly confirmed by experimentation.

In the scientific method, a hypothesis is an initial testable explanation. For a hypothesis to be elevated to the status of a scientific theory, it must be rigorously and repeatedly tested through experimentation and observation. A theory is a well-substantiated explanation that has been consistently confirmed by a vast body of empirical evidence.

Free NYSTCE Chemistry Questions and Answers

In general, how do atomic masses vary across the periodic table of elements?