Answer: There are 7.4 moles of helium gas present in a 1.85 liter container at the same temperature and pressure.
Explanation:
Given:
= 2.25 L,
= 9.0 mol
= 1.85 L,
= ?
Formula used to calculate the moles of helium are as follows.

Substitute the values into above formula as follows.

Thus, we can conclude that there are 7.4 moles of helium gas present in a 1.85 liter container at the same temperature and pressure.
Answer:
pH = 1.33
Explanation:
Because HCl is a strong acid, each mole of HCl will completely dissociate into H⁺ and Cl⁻ species.
Now we calculate the molar concentration (molarity) of H⁺:
- Molarity = moles / volume
(750 mL ⇒ 750 / 1000 = 0.750 L)
- Molarity = 0.035 moles / 0.750 L
Then we calculate the pH of the solution:
Se: Selenium
Protons: 34
Electrons: All atoms in the periodic table are neutral until changed otherwise
Neutrons: 44
Atomic Mass: 78.09
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