An atomic mass unit is equal to
a.
one-half the mass of a hydrogen atom.
b.
one-fourth the mass of a lithium atom.
c.
one-twelfth the mass of a carbon-12 atom.
d.
one-fifteenth the mass of a nitrogen-15 atom.

c.  one-twelfth the mass of a carbon-12 atom.

Explanation: An atomic mass unit ( amu) is defined as of the mass of an atom of carbon with mass number 12 , which is the most abundant isotope of carbon. Thus the carbon-12 atom has six protons and six neutrons in its nucleus.

1 amu is approximately equal to or . The mass of an atom in amu is roughly equal to the sum of the number of protons and neutrons in the nucleus.

amu is used to differentiate between isotopes as they would have different mass.

568.98

explanation:

its math

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂