Questions: Which of the following is not an example of a reaction requiring activation energy? - boiling water - photosynthesis - starting a car's engine - lighting a campfire In the equation 2 H2 + O2 → 2 H2O, what is the total number of hydrogen atoms on the reactant side? What is the purpose of the flame from a match in lighting a campfire?

Which of the following is not an example of a reaction requiring activation energy? - boiling water - photosynthesis - starting a car's engine - lighting a campfire In the equation 2 H2 + O2 → 2 H2O, what is the total number of hydrogen atoms on the reactant side? What is the purpose of the flame from a match in lighting a campfire?
Transcript text: Which of the following is not an example of a reaction requiring activation energy? boiling water photosynthesis starting a car's engine lighting a campfire In the equation $2 \mathrm{H}_{2}+\mathrm{O}_{2} \rightarrow 2 \mathrm{H}_{2} \mathrm{O}$, what is the total number of hydrogen atoms on the reactant side? What is the purpose of the flame from a match in lighting a campfire?
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Solution

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Solution Steps

Step 1: Identify the Reaction Not Requiring Activation Energy

To determine which of the given options does not require activation energy, we need to understand that activation energy is the minimum energy required to start a chemical reaction.

  • Boiling water: This is a physical change, not a chemical reaction, and does not require activation energy.
  • Photosynthesis: This is a chemical reaction that requires activation energy from sunlight.
  • Starting a car's engine: This involves combustion, a chemical reaction requiring activation energy.
  • Lighting a campfire: This is also a combustion reaction requiring activation energy.

Thus, the answer is boiling water.

\(\boxed{\text{boiling water}}\)

Step 2: Count the Hydrogen Atoms on the Reactant Side

In the equation \(2 \mathrm{H}_{2} + \mathrm{O}_{2} \rightarrow 2 \mathrm{H}_{2} \mathrm{O}\), we need to count the number of hydrogen atoms on the reactant side.

  • Each \(\mathrm{H}_{2}\) molecule contains 2 hydrogen atoms.
  • There are 2 \(\mathrm{H}_{2}\) molecules.

So, the total number of hydrogen atoms is: \[ 2 \times 2 = 4 \]

\(\boxed{4}\)

Step 3: Purpose of the Flame from a Match in Lighting a Campfire

The purpose of the flame from a match in lighting a campfire is to provide the activation energy needed to start the combustion reaction of the wood.

\(\boxed{\text{To provide activation energy}}\)

Final Answer

  1. The reaction not requiring activation energy is \(\boxed{\text{boiling water}}\).
  2. The total number of hydrogen atoms on the reactant side is \(\boxed{4}\).
  3. The purpose of the flame from a match in lighting a campfire is \(\boxed{\text{To provide activation energy}}\).
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