Week 4 Part 2 Explaining Chemical Reactions

Multiple Choice

Which of the following best describes a reactant in a chemical reaction?

• A substance that is produced during the reaction

• A substance that is present after the reaction

• A substance that takes part and undergoes change during the reaction

• A substance that remains unchanged after the reaction

Multiple Choice

What happens when particles and atoms collide with enough force during a chemical reaction?

• They bounce off each other without any change.

• They break apart and rearrange to form new combinations.

• They disappear completely.

• They lose energy and stop moving.

Multiple Select

Which of the following statements about chemical reactions is correct?

• Chemical reactions always produce new substances.

• Ineffective collisions result in the formation of new substances.

• Effective collisions can lead to the rearrangement of atoms and formation of new substances.

• Chemical reactions never involve the breaking of bonds.

Open Ended

Describe the difference between reactants and products in a chemical equation, using CH4 + O2 → CO2 + H2O as an example.

Multiple Choice

Which of the following is a product in the chemical reaction: CH4 + O2 → CO2 + H2O?

• CH4

• O2

• CO2

• H2

Multiple Choice

Why is the equation CH4 + O2 → CO2 + H2O not balanced?

• Because the number of atoms of each element is not equal on both sides

• Because the coefficients are missing

• Because the equation is missing a product

• Because the equation is missing a reactant

Open Ended

Explain the role of coefficients in balancing chemical equations.

Fill in the Blanks

Fill in the blank: To balance the equation CH4 + ___ O2 → CO2 + 2H2O, the coefficient for O2 should be ___.

Multiple Select

Which of the following statements are true about calculating the number of atoms in a balanced chemical equation?

• You multiply the coefficient by the subscript to get the number of atoms

• Coefficients are always equal to 1

• Subscripts can be ignored when balancing equations

• The number of atoms of each element must be equal on both sides

Multiple Choice

Which factor increases the rate of a chemical reaction according to the slides?

• Increase in the number and hardness of collisions

• Decrease in temperature

• Reduction in reactant concentration

• Addition of inert gases

Multiple Choice

Which of the following best explains why increasing temperature increases the rate of a chemical reaction?

• Particles move faster and collide more often.

• Particles become larger and heavier.

• Particles change color when heated.

• Particles lose energy as temperature increases.

Multiple Select

Select all the factors that increase the rate of reaction according to the images shown.

• Higher temperature

• Lower concentration

• Greater surface area

• Less space for collisions

Multiple Choice

Which term refers to the substance that undergoes change during a chemical reaction?

• Product

• Reactant

• Concentration

• Chemical formula

Multiple Choice

How many HCl molecules do you need to balance this equation? 
Mg +  __HCl --->  MgCl₂ + H₂

• 1
• 2
• 3
• 4

Multiple Choice

Is this balanced?
Al + O₂ → 2Al₂O₃

• Yes
• No

Multiple Choice

Is the following equation balanced?
2C₂H₂ + 5O₂ --> 4CO₂ + 2H₂O

• yes
• no

Multiple Choice

Is the following reaction balanced?
2CH₃OH + 3O₂ --> 2CO₂ + 4H₂O

• yes
• no

Multiple Choice

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO

Multiple Choice

Balance this equation:

H₂ + Cl₂ ---> HCl

• It is balanced.

• H₂ + Cl₂ ---> 2HCl

• 3H₂ + Cl₂ ---> 6HCl

• H₂ + 3Cl₂ ---> 6HCl

Multiple Choice

How many Oxygen atoms are in 2SO₄?

• 1

• 2

• 4

• 8

Multiple Choice

Determine the coefficients to make the following equation balanced?

__N₂ + __O₂--> __NO

• 1, 1, 1

• 1, 1, 2

• 2, 2, 2

• 1, 2, 2

Multiple Choice

What is the Law of Conservation of Mass?

• It states that matter cannot be created or destroyed.

• It states that energy cannot be created or destroyed.

• It states that matter can be created or destroyed.

• It states that sound can be created or destroyed.