Which element has the greatest density at stp?
(1) magnesium (3) barium
(2) beryllium (4) radium

Option (4) is the correct answer.

Explanation:

It is known that density is mass divided by volume.

Mathematically,       Density =

Since, density is directly proportional to mass. So, more is the mass of an element more will be its density.

Mass of magnesium is 24.305 g/mol.

Mass of barium is 137.327 g/mol.

Mass of beryllium is 9.012 g/mol

Mass of radium is  226 g/mol.

Hence, radium has more mass therefore it will have the greatest density at STP.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm