Assume the atmospheric pressure is 1 atm but the actual pressure is higher than 1 atm how will this error affect the calculated molar mass of the unknown

Answer : When we consider the atmospheric pressure as 1 atm then according to the ideal gas equation we can find out the molar mass of any unknown by this formula;

PV=nRT

so if the pressure increases than 1 atm then we can see from the above equation that it will result in greater value for the number of moles (n) in the above equation.

While n = m/M where m is mass of the unknown in g and M is molecular mass.

So, if pressure is higher then it will result in molar mass of unknown which is much smaller.