Over the last several decades, scientists have addressed the problem of nonrenewable natural resources such as fossil fuels. Hum
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Answer:
- Question 19: the three are molecular compounds.
- Question 20: CuSO₄.5H₂O
Explanation:
<em>Question 19.</em>
- C₂H₄
- HF
- H₂O₂
All of them are the combination of two kinds of different atoms in fixed proportions.
- C₂H₄: two carbon atoms per four hydrogen atoms
- HF: one hydrogen atom per one fluorine atom
- H₂O₂: two hydrogen atoms per two oxygent atoms
Thus, they all meet the definition of compund: a pure substance formed by two or more different elements with a definite composition.
Molecular compounds are formed by covalent bonds and ionic compounds are formed by ionic bonds.
Two non-metal elements, like H-F, C - C, C - H, H-O, H - H, and O - O will share electrons forming covalent bonds to complete their valence shell. Thus, the three compounds are molecular and not ionic.
<em>Question 20. </em>Formula of copper(II) sulfate hydrate with 36.0% water.
Copper(II) sulfate is CuSO₄. Its molar mass is 159.609g/mol
Water is H₂O. Its molar mass is 18.015g/mol
Calling x the number of water molecules in the hydrate, the percentage of water is:
From which we can solve for x:
Thus, there are 5 molecules of water per each unit of CuSO₄, and the formula is:
- CuSO₄.5H₂O
pH is the hydrogen ion concentration and pOH is the hydroxide ion concentration in the solution. pH KOH is 12.73, pOH KOH is 2.24 and pH NaCl is 7.
<h3>What are pH and pOH?</h3>pH is the negative log of the hydrogen ion concentration and pOH is the negative log of the hydroxide ion concentration.
The relation between the pH and pOH can be given as,
The pH of KOH can be calculated by the formula,
In the first case, the concentration of the KOH is
Substituting values in the equation:
Hence, the pH of KOH is 12.73.
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pOH of KOH can be calculated by the formula,
The hydroxide concentration of the KOH solution is
Substituting value in the equation:
Hence, the pOH of KOH is 2.24
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The pH of NaCl can be calculated by the formula,
In the third case, the concentration of the NaCl is
Substituting values in the equation:
Hence, the pH of KOH is 7.0.
Therefore, KOH is basic and NaCl is approximately neutral.
Learn more about pH and pOH here: