WorksheetsChapter 6 practice questions
Total questions: 65
Worksheet time: 2hrs 14mins
In a chemical equation, the substances on the left side of the arrow are called _______________.
reactants
products
catalysts
solvents
The numbers placed in front of chemical formulas to balance equations are called _______________.
coefficients
subscripts
reactants
products
The law that states mass cannot be created or destroyed in a chemical reaction is the law of _______________.
conservation of mass
definite proportions
multiple proportions
conservation of energy
The ratio of the coefficients of reactants and products in a balanced equation is called the _______________.
mole ratio
mass ratio
volume ratio
energy ratio
According to the law of _______________, a compound always contains the same elements in the same proportions.
definite proportions
multiple proportions
conservation of mass
conservation of energy
What must be the same on both sides of a balanced chemical equation?
The total number of molecules
The number of atoms of each element
The number of compounds
The number of products
Which of the following is a balanced equation for the combustion of methane?
CH4 + O2 → CO2 + H2O
2CH4 + O2 → 2CO2 + 2H2O
CH4 + 2O2 → CO2 + 2H2O
CH4 + O2 → 2CO2 + H2O
In the equation 2Mg + O2 → 2MgO, what is the mole ratio of Mg to O2?
1:1
2:1
1:2
2:2
Which of the following cannot be changed to balance a chemical equation?
The coefficients
The subscripts in formulas
The number of reactants
The number of products
If 2 moles of H2O are decomposed according to the equation 2H2O → 2H2 + O2, how many moles of H2 are formed?
1
2
3
4
It is important to balance chemical equations because:
it ensures the law of conservation of mass is followed.
it makes the equation look more complex.
it increases the number of products formed.
it changes the identity of the reactants.
A balanced chemical equation can be used to determine the amount of products formed from a certain amount of reactants by:
Using the coefficients to set up mole ratios.
Measuring the temperature change.
Observing the color change.
Estimating by visual inspection.
The law of definite proportions applies to the reaction 2Mg + O2 → 2MgO because:
Magnesium and oxygen always combine in a fixed mass ratio to form magnesium oxide.
The reaction can occur with any ratio of magnesium and oxygen.
The mass of magnesium oxide formed is always less than the total mass of reactants.
Oxygen is always in excess in this reaction.
How many Hydrogen atoms are in 4H2O?
6
8
2
4
How many Magnesium atoms are in 10MgCl2?
10
5
20
12
A subscript is the small number below the element symbol that tells the number of _______ of that element.
atoms
valence electrons
protons
elements
Balance this equation:
H2 + Cl2 ---> HCl
It is balanced.
H2 + Cl2 ---> 2HCl
3H2 + Cl2 ---> 6HCl
H2 + 3Cl2 ---> 6HCl
Balance this equation:
HgO ---> Hg + O2
It is balanced.
2HgO ---> 2Hg + O2
2HgO ---> Hg + O2
HgO ---> Hg + 2O2
Mg + __HCl ---> MgCl2 + H2
Which of the following is balanced?
Mg + HCl --> H2 + MgCl2
H2O + CO2 --> H2CO3
KClO3 --> KCl + O2
H2 + O2 --> H2O
What is the left part of a chemical equation called?
2H2 + O2 ---> 2H2O
Reactants
Yields
Products
Chemical equation
What number will balance the following chemical reaction?
S8+8O2→ _ SO2
1
4
8
16
Fill in the Blank: Fill in the blank with the correct words. 1. A ____________ is a substance that participates in a chemical reaction.
reactant
product
solvent
catalyst
When bonds between atoms are broken, ____________ is required.
energy
water
light
pressure
The production of heat and light when gasoline burns is an example of an ____________ reaction.
exothermic
endothermic
neutralization
decomposition
Photosynthesis is an example of an ____________ reaction because it absorbs energy.
endothermic
exothermic
combustion
decomposition
The new substances formed in a chemical reaction are called ____________.
products
reactants
elements
mixtures
Which of the following is NOT a sign that a chemical reaction is taking place?
Change in color
Change in shape
Production of a gas
Release of energy
What happens to atoms during a chemical reaction?
They disappear
They are rearranged
They turn into energy
They lose electrons
Which statement best describes an exothermic reaction?
It absorbs energy from the surroundings
It releases energy to the surroundings
It uses light to make food
It forms only gases
What is chemical energy?
Energy from the sun
Energy stored in the bonds of chemical compounds
Energy from movement
Energy from sound
When self-heating meals are activated, what type of chemical reaction is taking place?
Endothermic
Exothermic
Neutralization
Decomposition
Which of the following are signs that a chemical reaction may be taking place?
Change in color and formation of a gas
Increase in temperature and decrease in mass
Change in shape and increase in size
Movement and sound production
Which of the following best explains the difference between an endothermic and an exothermic reaction, and provides an example of each?
Endothermic reactions absorb heat (e.g., photosynthesis), while exothermic reactions release heat (e.g., combustion).
Endothermic reactions release heat (e.g., combustion), while exothermic reactions absorb heat (e.g., photosynthesis).
Both endothermic and exothermic reactions absorb heat (e.g., photosynthesis and combustion).
Both endothermic and exothermic reactions release heat (e.g., photosynthesis and combustion).
How does the rearrangement of atoms during a chemical reaction support the law of conservation of mass?
Because atoms are destroyed and created, changing the total mass.
Because atoms are rearranged but not created or destroyed, so the total mass remains the same.
Because atoms lose mass during reactions, decreasing the total mass.
Because atoms gain mass from energy, increasing the total mass.
Balance the following chemical equation: CuCl2 + Al → AlCl3 + Cu.
3 CuCl2 + 2 Al → 2 AlCl3 + 3 Cu.
CuCl2 + Al → AlCl2 + Cu.
2 CuCl2 + 2 Al → 2 AlCl3 + 2 Cu.
3 CuCl2 + 3 Al → 2 AlCl3 + 3 Cu.
Which of these is not a sign of a chemical reaction?
A gas is given off.
The material dissolves.
Heat is released.
A color change occurs.
The substance that is formed in a chemical reaction is called the
polymer.
reactant.
radical.
product.
Which of the following stores chemical energy?
the temperature of a substance
the density of a substance
the bonds of a molecule
the nucleus of an atom
Which of the following occurs in an endothermic reaction but not in an exothermic reaction?
Chemical bonds are broken.
Energy is absorbed.
Molecules are formed.
Atoms are rearranged.
A type of reaction that produces an increase in temperature is
endothermic.
exothermic.
covalent.
nonpolar.
An example of an endothermic reaction is
bioluminescence by a firefly.
an exploding firecracker.
burning gasoline.
photosynthesis by a plant.
A reaction in which the products contain more chemical energy than the reactants is
exothermic.
electrical.
endothermic.
exergonic.
Which of these represents the release of chemical energy?
pouring gasoline into a tank
burning charcoal in a grill
a toy car running down a ramp
warming food in a microwave
Which of the following are the products and reactants of a chemical reaction most likely to have in common?
atoms
molecules
physical properties
chemical properties
Which of the following occurs when gasoline is burned?
New elements are formed.
New atoms are formed.
New molecules are formed.
all of the above
In a ______________ reaction, two or more substances combine to form a new compound.
synthesis
decomposition
single replacement
combustion
______________ reactions break down a compound into simpler substances.
Decomposition
Combination
Displacement
Neutralization
In a combustion reaction, a substance reacts with ______________ to release energy.
oxygen
hydrogen
carbon dioxide
nitrogen
In a ____________ reaction, one element takes the place of another in a compound.
single displacement
double displacement
synthesis
decomposition
In a __________ reaction, ions appear to be exchanged between compounds.
single displacement
double displacement
combustion
oxidation-reduction
A radical is ______ and it is so reactive because ______.
a molecule with an extra proton; it is unstable
an atom or molecule with an unpaired electron; it seeks to pair its electron
a molecule with a double bond; it is highly energetic
an ion with a negative charge; it attracts positive ions
Predict the products of this reaction: The decomposition of CaCO3. What type of reaction is this?
CaO and CO2; Decomposition reaction
Ca and CO3; Synthesis reaction
CaCO and O2; Redox reaction
CaO2 and CO; Displacement reaction
The transfer of electrons in a redox reaction differs from the sharing of electrons in a covalent bond in which of the following ways?
Electrons are transferred in redox reactions, while they are shared in covalent bonds.
Electrons are shared in redox reactions, while they are transferred in covalent bonds.
Both involve only the sharing of electrons.
Both involve only the transfer of electrons.
The decomposition of water can be brought about by
combustion.
electrolysis.
synthesis reactions.
oxidation.
In an oxidation-reduction reaction,
both substances gain electrons.
both substances lose electrons.
one substance gains, the other loses electrons.
substances that give up electrons are reduced.
Which of the following represents a double-displacement reaction between sodium chloride and silver fluoride?
NaCl + AgF → NaAgF + Cl₂
NaCl + AgF → NaF + AgCl
NaCl + AgF → Ag + NaClF
NaCl + AgF → NaF + Cl₂ + Ag
Pieces of molecules that have one or more electrons available for bonding are
radicals.
reactants.
neutrons.
protons.
A synthesis reaction between magnesium (Mg) and oxygen (O₂) might produce
Mg₂.
O₄.
MgO.
MgCO₂.
What type of reaction? CH₄ + 2O₂ → CO₂ + 2H₂O
synthesis reaction
decomposition reaction
combustion reaction
single-displacement reaction
double-displacement reaction
What type of reaction? 2NH₃ → N₂ + 3H₂
synthesis reaction
decomposition reaction
combustion reaction
single-displacement reaction
double-displacement reaction
What type of reaction? 2NaCl + H₂SO₄ → Na₂SO₄ + 2HCl
synthesis reaction
decomposition reaction
combustion reaction
single-displacement reaction
double-displacement reaction
What type of reaction? Fe + S → FeS
synthesis reaction
decomposition reaction
combustion reaction
single-displacement reaction
double-displacement reaction
What type of reaction? 2Li + 2H₂O → 2LiOH + H₂
synthesis reaction
decomposition reaction
combustion reaction
single-displacement reaction
double-displacement reaction
