Rusting iron is an example of a chemical change because iron reacts with air when moisture is present.
examples of chemical changes are:
• Molecules rearrange with other molecules to make new substance
• Can be production of flames
• Color change
• Bubbling/fizzing
• Temp. change
Examples of physical changes are:
• Melting
• Boiling
• Freezing
• Condensing
• Breaking
• Bending
• Dissolving
Heating the reaction flask on a hot plate is an example of supplying activation energy to begin a reaction.
Explanation:
<u>Definition:</u>
Activation energy is defined as the minimum amount of energy required to start a particular chemical reaction.
For example: When hydrogen and oxygen are mixed together it does not immediately start the reaction to form water. So, to start the reaction a small electric spark is provided or it is heated to provide some energy. This energy causes the molecules of hydrogen and water to react, thus producing even more molecules to react and finally water is formed.
Here the electric spark or the heat provided is the activation energy.
<span>Because
the question is asking moles of NH3, the compound, any subscripts are
irrelevant. It only wants to know how many moles of NH3 molecules, not
individual atoms.
Therefore, we can simply convert to moles. 1.5x10^23/6.022x10^23 = .249 moles of NH3.
(If it were to ask moles of Hydrogen, for example, you would multiply
the answer by 3, because there are 3 atoms of Hydrogen per one molecule
of NH3. But this only asks for moles of the entire compound).
hope you have a great day! :)
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27g x 1cm^2/2.7g = answer in cm^2
Grams cancel out