A gas occupies 2.50 L at 1.5 atm. What will be the volume of this gas if the pressure becomes 1.25 atm?

0.067M H3PO4

Explanation:

H3PO4 reacts with NaOH as follows:

H3PO4 + 3NaOH → 3H2O + Na3PO4

Where 1 mole of H3PO4 reacts with 3 moles of NaOH

To solve trhis question we need to find the moles of NaOH required. With the chemical equation we can find the moles of H3PO4 and its concentration as follows:

Moles NaOH:

50.0mL = 0.0500L * (0.20moles /L) = 0.0100 moles NaOH

Moles H3PO4:

0.0100 moles NaOH * (1mol H3PO4 / 3mol NaOH) = 0.00333 moles H3PO4

Concentration:

0.00333 moles H3PO4 / 0.0500L = 0.067M H3PO4