ED - Factors affecting Rate of Reaction

What is the rate of reaction if the product concentration increases by 0.4 M in 4 hours?

• 0.1 M/hr

• 0.2 M/hr

• 0.05 M/hr

• 0.4 M/hr

Answer explanation

The rate of reaction is calculated by dividing the change in concentration by the time taken. Here, 0.4 M increase in 4 hours gives a rate of 0.4 M / 4 hr = 0.1 M/hr, which is the correct answer.

Tags

NGSS.HS-PS1-5

Which event must always occur for a chemical reaction to take place?

• formation of a precipitate

• formation of a gas

• effective collisions between reacting particles

• addition of a catalyst to the reaction system

Answer explanation

For a chemical reaction to occur, there must be effective collisions between reacting particles. This ensures that the necessary energy and orientation for the reaction are present, making it the essential requirement.

Increasing the temperature increases the rate of a reaction by

• lowering the activation energy

• increasing the activation energy

• lowering the frequency of effective collisions between reacting molecules

• increasing the frequency of effective collisions between reacting molecules

Answer explanation

Increasing the temperature raises the kinetic energy of molecules, leading to more frequent and effective collisions. This enhances the reaction rate, making 'increasing the frequency of effective collisions between reacting molecules' the correct choice.

Tags

NGSS.HS-PS1-5

The energy needed to start a chemical reaction is called

• potential energy

• kinetic energy

• activation energy

• ionization energy

Answer explanation

The energy needed to start a chemical reaction is known as activation energy. It is the minimum energy required for reactants to undergo a transformation into products.

Tags

NGSS.HS-PS1-4

Given the reaction: Mg + 2 H2O → Mg(OH)2 + H2, at which temperature will the reaction occur at the greatest rate?

• 25°C

• 50°C

• 75°C

• 100°C

Answer explanation

The reaction rate increases with temperature due to higher kinetic energy of molecules. At 100°C, the increased energy enhances the frequency and energy of collisions, leading to the greatest reaction rate.

Tags

NGSS.HS-PS1-5

A piece of Mg(s) ribbon is held in a Bunsen burner flame and begins to burn according to the equation: 2Mg(s) + O2(g) → 2MgO(s). The reaction begins because the reactants

• are activated by heat from the Bunsen burner flame

• are activated by heat from the burning magnesium

• underwent an increase in entropy

• underwent a decrease in entropy

Answer explanation

The reaction starts because the heat from the Bunsen burner flame activates the reactants, allowing magnesium and oxygen to react and form magnesium oxide. This heat is essential for overcoming the activation energy barrier.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-4

As the number of effective collisions between reacting particles increases, the rate of reaction

• decreases

• increases

• remains the same

Answer explanation

As the number of effective collisions increases, more particles successfully react, leading to a higher rate of reaction. Therefore, the correct answer is that the rate of reaction increases.

Tags

NGSS.HS-PS1-5

Which conditions will increase the rate of a chemical reaction?

• decreased temperature and decreased concentration of reactants

• decreased temperature and increased concentration of reactants

• increased temperature and decreased concentration of reactants

• increased temperature and increased concentration of reactants

Answer explanation

Increasing temperature raises the energy of particles, leading to more frequent and effective collisions. Higher concentration of reactants also increases the likelihood of collisions, thus accelerating the reaction rate.

Tags

NGSS.HS-PS1-5

Base your answer to the following question on the table below, which represents the production of 50 milliliters of CO2 in the reaction of HCl with NaHCO3. Five trials were performed under different conditions as shown. (The same mass of NaHCO3 was used in each trial.) Which two trials could be used to measure the effect of surface area?

• trials A and B

• trials A and C

• trials A and D

• trials B and D

Answer explanation

Trials A and B can be used to measure the effect of surface area because they differ in the physical form of NaHCO3, affecting how quickly it reacts with HCl, while keeping the mass constant.

Tags

NGSS.MS-PS1-2

Base your answer to the following question on the table below, which represents the production of 50 milliliters of CO2 in the reaction of HCl with NaHCO3. Five trials were performed under different conditions as shown. (The same mass of NaHCO3 was used in each trial.) Which two trials could be used to investigate the effect of concentration of solutions?

• trials A and B

• trials A and C

• trials C and E

• trials B and D

Answer explanation

Trials C and E vary the concentration of HCl while keeping the mass of NaHCO3 constant, allowing for the investigation of concentration effects. Other trials do not provide this variation.

Tags

NGSS.HS-PS1-5