Answer:
B
Explanation:
Recall the law of effusion:

Because 5 mol of oxygen was effused in 10 seconds, the rate is 0.5 mol/s.
Let the rate of oxygen be <em>r</em>₁ and the rate of hydrogen be <em>r</em>₂.
The molecular weight of oxygen gas is 32.00 g/mol and the molecular weight of hydrogen gas is 2.02 g/mol.
Substitute and solve for <em>r</em>₂:

Because there are 5 moles of hydrogen gas:

In conclusion, it will take about 2.5 seconds for the hydrogen gas to effuse.
Check: Because hydrogen gas is lighter than oxygen gas, we expect that hydrogen gas will effuse quicker than oxygen gas.
Answer:
I think its B im not sure
but i hope this helps
Ca(OH)₂ ==> Ca²⁺ + 2 OH<span>-
Ca(OH)</span>₂ is <span>strong Bases</span><span>
</span>Therefore, the [OH-] equals 5 x 10⁻⁴ M. For every Ca(OH)₂ you produce 2 OH⁻<span>.
</span>
pOH = - log[ OH⁻]
pOH = - log [ <span>5 x 10⁻⁴ ]
pOH = 3.30
pH + pOH = 14
pH + 3.30 = 14
pH = 14 - 3.30
pH = 10.7
hope this helps!</span>