Q: A molecule of water contains two hydrogen atoms and one oxygen atom. What is the molar mass of water ($$H_2O$$)? (Atomic masses: H = 1.008 g/mol, O = 15.999 g/mol)

$$2 \times 1.008 + 15.999 = 18.015 g/$$mol

Question 1

Which of the following best describes the difference between a compound and an element, according to the matter flowchart?

Accepted Answer

A compound can be chemically decomposed into simpler substances, while an element cannot.

Question 2

Which of the following is a correct statement about isotopes, as illustrated by the hydrogen isotopes (protium, deuterium, tritium)?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 3

A sample contains only one type of atom and cannot be chemically decomposed. According to the matter flowchart, this sample is best classified as:

Accepted Answer

An element

Question 4

Which of the following statements about electrical charges is correct?

Accepted Answer

Like charges repel and opposite charges attract.

Question 5

Given the atomic structure of boron shown, which isotope is more abundant in nature?

Accepted Answer

Boron-11

Question 6

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same proportions by mass.

Question 7

Which of the following is the correct formula for calculating the kinetic energy of an object?

Accepted Answer

$$E_K = \frac{1}{2}mv^2$

Question 8

A molecule of water contains two hydrogen atoms and one oxygen atom. What is the molar mass of water ($$H_2O$$)? (Atomic masses: H = 1.008 g/mol, O = 15.999 g/mol)

Accepted Answer

$$2 	imes 1.008 + 15.999 = 18.015 g/$$mol

Question 9

Which of the following best explains why the nucleus of an atom does not fly apart due to the repulsion between protons?

Accepted Answer

The strong nuclear force holds the protons and neutrons together.

Question 10

A sample of carbon dioxide ($$CO_2) $$has a mass of 88.018 g. How many moles of $$CO_2$$ are present? (Molar mass of $$CO_2 = 44.009$ g/mol)

Accepted Answer

$$88.018 \div 44.009 = 2.00$$ moles

Question 11

Which of the following is true about ions?

Accepted Answer

Cations are atoms that have lost electrons.

Question 12

Which of the following is the correct SI unit for energy?

Accepted Answer

Joule (J)

Question 13

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with a uniform composition throughout

Question 14

Which of the following is a correct statement about the photoelectric effect?

Accepted Answer

Only one photon at a time can interact with a given electron, transferring all its energy.

Question 15

If a nucleus has a high neutron-to-proton ratio, which type of decay is it most likely to undergo?

Accepted Answer

Beta decay

Question 16

Which of the following is the correct expression for the energy of a photon according to the Planck-Einstein relationship?

Accepted Answer

$$E = hv$$

Question 17

A molecule contains 6 carbon atoms, 6 hydrogen atoms, 1 nitrogen atom, and 2 oxygen atoms. If the atomic masses are: C = 12.01 g/mol, H = 1.008 g/mol, N = 14.01 g/mol, O = 16.00 g/mol, what is the molar mass of the molecule?

Accepted Answer

$$6 	imes 12.01 + 6 	imes 1.008 + 14.01 + 2 	imes 16.00 = 108.10 g/$$mol

Question 18

Which of the following is NOT a core concept underpinning chemistry as described in the study materials?

Accepted Answer

Color determines reactivity

Question 19

Which of the following best describes the difference between kinetic and potential energy?

Accepted Answer

Kinetic energy is energy of motion, while potential energy is stored energy due to position.

General Chemistry Study Notes: Atomic Structure, Matter Classification, and Energy

Guida di studio - Domande di pratica

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