Some hydrogen gas is collected over water at 20.0°C. The levels of water inside and outside the gas-collection bottle are the same. The partial pressure of hydrogen is 742.5 torr. What is the barometric pressure at the time the gas is collected?

Answer : The barometric pressure at the time the gas collected is, 760 mmHg

Explanation :

According to the Dalton's Law of partial pressure, the total pressure of a  mixture of gases is equal to the sum of the partial pressures  of the component gases.

where,

= total pressure

= partial pressure of hydrogen gas = 742.5 mmHg

= partial pressure of water vapor at = 17.5 mmHg  (standard value)

Now put all the given values in the above expression, we get:

Therefore, the barometric pressure at the time the gas collected is, 760 mmHg

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error