Practice Questions Chemistry

Chemical Equations

By CL Frick

Multiple Choice

How many protons does this atom have?

• 1

• 7

• 14

• 21

Multiple Choice

Which sentence best describes the atom in the diagram?

• It has no charge.

• It has more electrons than protons

• It is a hydrogen atom.

• Each of its neutrons has a positive charge

Multiple Choice

What is the name of this atom?

• hydrogen

• carbon

• nitrogen

• francium

Multiple Choice

An atom has an equal number of positively-charged

protons and negatively-charged electrons. If an atom loses or gains electrons, it changes from a neutral atom to an ion. Why is it clear that the model represents a carbon

atom, not a carbon ion?

• The nucleus has same number of protons and neutrons

• The number of electrons equals half the number of particles in the nucleus

• The number of electrons equals the number of protons

• The particle has a charge

Multiple Choice

Which statement describes this oxygen ion?

• It is negatively charged

• It is positively charged

• It resulted from an atom gaining 2 protons

• It resulted from an atom losing 2 neutrons

Multiple Choice

In addition to ionic bonds, atoms can also form bonds by sharing electrons. These are called covalent bonds, and the covalent compounds that they create have a fixed ratio of atoms. For example, carbon dioxide (CO₂) consists of one carbon atom and two oxygen atoms sharing electrons. In scientific models, these bonds are represented by lines or rods. The names of these compounds contain prefixes that indicate the number of a specific atom. For example, "di" means 2. Based on the passage and the image, what does dioxide mean?

• made up of carbon and oxygen

• having 3 atoms

• containing oxygen

• having 2 oxygen atoms

Multiple Choice

What does each circled plus sign represent?

• electron cloud of a hydrogen atom

• the single electron of a hydrogen atom

• the addition of one atom to another to form a molecule

• the single proton in the nucleus of a hydrogen atom

Multiple Choice

What does the stick in the ball-and-stick model represent?

• rod-like structures in the molecule

• movement of the atoms

• atomic nuclei

• a covalent bond between the atoms

Multiple Choice

Both models show that a hydrogen (H) molecule is formed when

• 2 hydrogen atoms share electrons

• 1 hydrogen atom loses an electron

• 1 hydrogen atom gains an electron

• 1 hydrogen atoms are connected by a rod

Multiple Choice

An ionic bond forms when electrons are tranferred from one atom to another. One atom gives up one or more electrons to another atom becomes a positively charged ion. The atom that receives the electron becomes a negatively charged ion. These compounds are called ionic compounds, or salts. Sodium and chlorine form sodium chloride, or table salt, through ionic bonding. Which statement describes the bond in sodium chloride?

• sodium and chlorine share electrons

• one electron is transferred from sodium to chlorine

• one electron is transferred from chlorine to sodium

• electrons move back and forth between the 2 atoms

Multiple Choice

Why does the sodium ion have a plus sign?

• an electron has been added

• sodium has more protons than chlorine

• the sodium ion lost an electron and now has a positive charge

• Any compound containing sodium has an electrical charge

Multiple Choice

Alkali metals (Group 1) share a variety of properties. They are soft, pliable, and conduct heat and electricity. They melt at relatively low temperatures and can explode if they become wet.

Which alkali metal melts at the lowest temperature?

• lithium

• potassium

• rubidium

• francium

Multiple Choice

What pattern does the information in the table suggest?

• the greater atomic weight, the lower the melting point

• the smaller the atomic weight, the lower the melting point

• the greater atomic number, the higher the melting point

• the greater the atomic number, the smaller the atomic weight

Multiple Choice

Matter cannot be destroyed or created when a chemical reaction occurs. Substances on the left are called the reactants. The newly formed substances on the right are called products. If the number of atoms of each element is the same on both sides of the equation, then the equation is balanced.

Is this equation for water balanced?

• Yes because there are 2 hydrogen atoms on both sides of the equation

• No because there are 2 oxygen atoms in the reactants and only one in the product.

• Yes. There are 2 oxygen atoms and 4 hydrogen atoms in the reactants and in the products

• No because the oxygen atoms have a smaller mass than the hydrogen atoms.