Answer: The reaction is exothermic reaction as the energy of products is less than the energy of reactants.
Explanation: Exothermic reactions are defined as the reactions in which energy of the product is less than the energy of the reactants. The total energy is released in the form of heat and 
for the reaction comes out to be negative.
Labeling of the parts in the diagram:
A represents the activation energy which is the energy required by reactants to cross the energy barrier to get converted to products.
E represents the potential energy of the reactants.
B represents the activated complex.
D represents the potential energy of the products.
C represents the total enthalpy change of the reaction, which comes out to be negative for exothermic reactions.
The first reason to repeat experiments is simply to verify results. Different science disciplines have different criteria for determining what good results are. Biological assays, for example must be done in at least triplicate to generate acceptable data. Science is built on the assumption that published experimental protocols are repeatable.
2) The next reason to repeat experiments is to develop skills necessary to extend established methods and develop new experiments. “Practice make perfect” is true for the concert hall and the chemical laboratory.
3) Refining experimental observations is another reason to repeat. Maybe you did not follow the progress of the reaction like you should have.
4) Another reason to repeat experiments is to study and/or improve them in way. In the synthetic chemistry laboratory, for example, there is always a desire to improve the yield of a synthetic step. Will certain changes in the experimental conditions lead to a better yield? The only way to find out is to try it! The scientific method informs us that it is best to only make one change at a time.
5) The final reason to repeat an extraction, chromatographic or synthetic protocol is to produce more of your target substance. This is sometimes referred to scale-up.
Answer:
5.41 ×10⁻²²
Explanation:
We were told right from the question that both the Zinc ions and the Zinc oxide adopts a face-centered cubic arrangement.
Then, the number of ZnO molecule in one unit cell = 4
The standard molar mass of ZnO = 81.38g
Avogadro's constant = 6.023 × 10²³ mole
∴
The mass of one unit cell of zinc oxide can be calculated as:
= 
= 5.40461564×10⁻²²
≅ 5.41 ×10⁻²²
∴ The mass of one unit cell of zinc oxide = 5.41 ×10⁻²²
Answer:
Coal
Explanation:
Coal is composed of the remains of dead animals and plants, being pressed down over the course of thousands of years.
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