7. a rectangular block of lead (pb) measures 20.0 mm x 30.0 mm x 45.0 mm. if the density of pb is 11.34 g/cm3, calculate the mass of the block.

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

it's c. elements are placed in rows based on how may valencies electrons have.