Which of these is a reason gold is more expensive than metals like aluminum? a) gold is rarely found in earth’s crust. b) gold is the most common metal on earth. c) gold is one of the lightest metals known to man. d) gold can easily be bent into attractive shapes and designs.

d

gold is very malleable and it doesn't tarnish/rust so it stays pretty

the correct answer is A. gold is the least metal found in the crust.

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation:

there is none because earth is stationary and flat.