a sealed vessel contains 15 kpa chlorine and 89 kpa fluorine in addition to some helium. the total pressure…

Explanation:

Step1: Recall Dalton's law

According to Dalton's law of partial - pressures, the total pressure ($P_{total}$) of a gas mixture is the sum of the partial pressures of its components. Let $P_{He}$ be the partial pressure of helium, $P_{Cl_2}$ be the partial pressure of chlorine, and $P_{F_2}$ be the partial pressure of fluorine. So, $P_{total}=P_{He}+P_{Cl_2}+P_{F_2}$.

Step2: Rearrange the formula to solve for $P_{He}$

We can rewrite the formula as $P_{He}=P_{total}-P_{Cl_2}-P_{F_2}$.

Step3: Substitute the given values

We know that $P_{total} = 205$ kPa, $P_{Cl_2}=15$ kPa, and $P_{F_2}=89$ kPa. Then $P_{He}=205 - 15-89$. $P_{He}=101$ kPa

Answer:

101 kPa