General Chemistry Study Guidance: Isotopes, Energy Conversion, and Chemical Bonding

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Topic: Isotopes and Average Atomic Mass

This question tests your understanding of how to calculate the abundance of isotopes using their masses and the average atomic mass of an element.

Isotope: Atoms of the same element with different numbers of neutrons (and thus different masses).
Average Atomic Mass: The weighted average of the masses of all isotopes of an element, based on their natural abundances.

Key formula:

Assign variables to the abundances: Let be the abundance of , for (given as 0.3%), and for .
Recall that the sum of all abundances must equal 100%: .
Write the average atomic mass equation using the given masses and abundances:
Note: Abundances should be expressed as decimals (e.g., 0.003 for 0.3%).
Substitute the known value for (0.3%) and express in terms of using the sum equation.
Set up the equations for and and prepare to solve for using algebra.

By substituting the values and solving the system of equations, the abundance of is approximately 90.4%.

This matches answer choice c.) (90.4 ± 0.3)%.

Topic: Energy Conversion

This question tests your understanding of different forms of energy and how they are transformed in physical processes.

Electrical Energy: Energy from the flow of electric charge.
Kinetic Energy: Energy of motion.
Potential Energy: Stored energy due to position (e.g., gravitational potential energy).

Consider what happens when an electric motor lifts an object: The motor uses electrical energy to operate.
As the object is raised, it gains height, which increases its gravitational potential energy.
Think about the energy transformation: Is the electrical energy being converted to kinetic energy (motion) or potential energy (position)?
Review the answer choices and match the correct energy conversion based on the process described.

The electric motor converts electrical energy into potential energy as the object is raised and its height increases.

Topic: Chemical Bonding

This question tests your understanding of the types of chemical bonds that form between elements, particularly between nonmetals.

Covalent Bond: A bond formed when two atoms share electrons, typically between nonmetals.
Ionic Bond: A bond formed when one atom donates electrons to another, typically between a metal and a nonmetal.
Metallic Bond: A bond formed between metal atoms, involving a 'sea' of shared electrons.

Identify the types of elements involved: Selenium (Se) and oxygen (O) are both nonmetals.
Recall the types of bonds that typically form between nonmetals: Covalent bonds are common.
Consider whether either element is a metal, which would suggest an ionic or metallic bond.
Review the answer choices and select the bond type that matches the elements involved.

Selenium and oxygen are both nonmetals, so they form covalent bonds by sharing electrons.