Question is incomplete, the complete question is as follows:
A student wants to examine a substance by altering the bonds within its molecules. Which of the following properties of the substance should the student examine?
A. Toxicity, because it can be observed by altering the state of the substance
B. Boiling point, because it can be observed by altering the state of the substance
C. Toxicity, because it can be observed by replacing the atoms of the substance with new atoms
D. Boiling point, because it can be observed by replacing the atoms of the substance with new atoms
Answer:
B.
Explanation:
A student can examine a substance without altering the bonds within the molecules by examining its boiling point.
The boiling point is the property of a substance, at which the substance changes its state, which is from solid to liquid, liquid to gas and others. So, examining the boiling point will alter the bonds within the molecules as the state of substance will change.
Hence, the correct answer is "B".
The reactions are in order which includes combustion reaction, Hydration reaction, oxidation reaction, and displacement reaction.
a) A combustion reaction is a chemical reaction between a fuel and an oxidant where heat is released. The combustion reaction example is given below. It is a balanced chemical reaction.
2C₃H₆(g) + 9O₂(g) --------> 6CO₂(g) + 6H₂O(g)
b. A hydration reaction is a chemical reaction in which a molecule of water is added to another molecule. Here Aluminum oxide is added to water to form aluminum hydroxide.
4Al₂O3(s) + 6H₂O(l)------> 2Al(OH)3(s)
c. When a metal reacts with oxygen, the metal forms an oxide. Oxide is a compound of metal and oxygen. Here lithium metal reacts with oxygen to form lithium oxide.
2Li(s) + O₂(g)-----> Li₂O(s)
d. A displacement reaction is one in which a more reactive element displaces a less reactive element from a compound. Here Zinc is more reactive than silver, so silver was displaced to form Zinc Nitrate.
Zn(s) + 2AgNO₃(aq) -----> 2Ag(s) + Zn(NO₃)₂(aq)
To know more about reactions, click below:
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Answer: the heat content of a system at constant pressure.
Explanation:
Enthalpy is defined as the heat content of a system at constant pressure.
It is the heat absorbed or released during a reaction at constant pressure,denoted as ΔH.
Heat energy is required.
In distillation, the solution is first heated, where heat energy is required, such as using a bunsen burner.
When the solution is heated, the water may reach its boiling point and evaporate. However, salt does not. When water molecules evaporates, it travels through a condenser that cools it down into liquid again. Therefore we get pure water. Salt is also obtained in the original beaker.
Therefore to first start this process, heat energy is required.
