Answer:
<h3>The answer is option A</h3>
Explanation:
To find the number of moles in a substance given it's number of entities we use the formula
where n is the number of moles
N is the number of entities
L is the Avogadro's constant which is
6.02 × 10²³ entities
From the question we have
We have the final answer as
<h3>2.99 moles</h3>
Hope this helps you
The temperature at which phase changes occur is highly dependent on the electrostatic forces between the molecules in the substance.
The forces that hold molecules together are called intermolecular forces. These intermolecular forces affect the temperature at which phase changes occur. The statement about phase changes and electrostatic forces that is correct is that; "the temperatures at which a substance changes phases indicate the relative strength of the forces between molecules in the substance."
There are three states of matter, solid liquid and gas. The order of intermolecular forces in all the states of matter are not the same. The order of strongest collective electrostatic forces to weakest collective electrostatic forces is; solid, liquid, gas.
When water boils, the forces between water molecules break, and the bonds between the atoms in water are unchanged.
When a sample of calcium carbonate is cooled, the forces strengthen, and the molecule structure becomes more rigid.
If the boiling point of acetone is lower than the boiling point of ethanol, then, the intermolecular forces in ethanol are stronger than the intermolecular forces in acetone.
Learn more about phase changes: brainly.com/question/671212
The concentration of the hydronium ion in hydrochloric acid is 0.0045 M, and the pH of the solution is 2.34.
<h3>What is pH?</h3>
pH is the potential of the hydrogen or the hydronium ions in the aqueous solution.
As the solution contains 
HCl the concentration of the hydronium ion will be the same, 
The pH of the solution is calculated as:
![\begin{aligned} \rm pH &= \rm -log[H^{+}]\\\\&= - \rm log (4.5 \times 10^{-3})\\\\&= 2.34\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%20%5Crm%20pH%20%26%3D%20%5Crm%20-log%5BH%5E%7B%2B%7D%5D%5C%5C%5C%5C%26%3D%20-%20%5Crm%20log%20%284.5%20%5Ctimes%2010%5E%7B-3%7D%29%5C%5C%5C%5C%26%3D%202.34%5Cend%7Baligned%7D)
The concentration of the hydroxide ion is calculated from pH and hydronium ion as:
![\begin{aligned} \rm [H_{3}O^{+}][OH^{-}] &= 10^{-14}\\\\&= \dfrac{1 \times 10^{-14}}{4.5 \times 10^{-3}}\\\\&= 2.2 \times 10^{12}\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%20%5Crm%20%5BH_%7B3%7DO%5E%7B%2B%7D%5D%5BOH%5E%7B-%7D%5D%20%26%3D%2010%5E%7B-14%7D%5C%5C%5C%5C%26%3D%20%5Cdfrac%7B1%20%5Ctimes%2010%5E%7B-14%7D%7D%7B4.5%20%5Ctimes%2010%5E%7B-3%7D%7D%5C%5C%5C%5C%26%3D%202.2%20%5Ctimes%2010%5E%7B12%7D%5Cend%7Baligned%7D)
Now, for the calcium hydroxide solution, the calculations are shown as,
pOH is calculated as:
![\begin{aligned} \rm pOH &= 14- 8 = 6\\\\\rm [OH^{-}] &= \rm antilog (-6)\\\\&= 10^{-6} \end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%20%5Crm%20pOH%20%26%3D%2014-%208%20%3D%206%5C%5C%5C%5C%5Crm%20%5BOH%5E%7B-%7D%5D%20%26%3D%20%20%5Crm%20antilog%20%28-6%29%5C%5C%5C%5C%26%3D%2010%5E%7B-6%7D%20%5Cend%7Baligned%7D)
The concentration of calcium hydroxide is calculated as:
![\begin{aligned} &= \dfrac{1}{2} \times \rm [OH^{-}]\\\\&= 5 \times 10^{-4} \;\rm M\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%20%26%3D%20%5Cdfrac%7B1%7D%7B2%7D%20%5Ctimes%20%5Crm%20%5BOH%5E%7B-%7D%5D%5C%5C%5C%5C%26%3D%205%20%5Ctimes%2010%5E%7B-4%7D%20%5C%3B%5Crm%20M%5Cend%7Baligned%7D)
Therefore, the pH and the pOH give the concentration of the hydrogen or the hydronium ion and the hydroxide ion.
Learn more about pH and pOH here:
brainly.com/question/16062632
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