Answer:
12.9 m³ is the new volume
Explanation:
As the temperature keeps on constant, and the moles of the gas remains constant too, if we decrease the pressure, the volume will increase. If the volume is decreased, pressure will be higher.
The relation is this: P₁ . V₁ = P₂ . V₂
1 atm . 0.93m³ = 0.072 atm . V₂
0.93m³ .atm / 0.072 atm = V₂
V₂ = 12.9 m³
In conclusion and as we said, pressure has highly decreased so volume has highly increased.
Answer : The mass of sodium bromide added should be, 18.3 grams.
Explanation :
Molality : It is defined as the number of moles of solute present in kilograms of solvent.
Formula used :

Solute is, NaBr and solvent is, water.
Given:
Molality of NaBr = 0.565 mol/kg
Molar mass of NaBr = 103 g/mole
Mass of water = 315 g
Now put all the given values in the above formula, we get:


Thus, the mass of sodium bromide added should be, 18.3 grams.
The units for molarity is moles of solute per liter of solution which means if you multiply the molarity of a solution by its volume you get how many moles of solute are in the solution. (0.75Mx0.5L=0.375mol NaCl)
Then you can multiply the moles of sodium chloride (0.375 mol) by its molar mass (58.45 g/mol) to get 21.92g of sodium chloride. That means there is 21.92 grams of sodium chloride in 500mL of 0.75M solution. I hope this helps. Let me know if anything is unclear.