Question

Calculate the mass of 1 mole of the following compounds ( round each element to nearest 0.5 AMU , then add them ) :

a. potassium fluoride KF

b. Iron II Hydroxide Fe(OH)2

c. Beta Hydroxybutyric acid C4H803

Answer 1

Answer: 1 mole molecular mass is calculated as adding of individual atoms/elements atomic mass of a molecule and expressed as atomic mass unit (amu) or grams/mole)

a. KF

1 mole of KF is calculated as : Molecular mass of K(39.0) + F (18.9)
= 39+19
=58 amu or grams/mole

b. Fe(OH)2  

= 1 atom of Fe + 2 atoms of oxygen + 2 atoms of hydrogen

=55.8+ 15.9 *2 + 2*1 (substituting individual aomic mass round off to nearest value)    * multiply

= 56+16*2+2 (rounding off to nearest value)

=56+32+2

=90 amu (Answer)

c. Beta Hydroxybutyric acid C4H803

= 4 atoms of carbon+ 8 atoms of hydrogen + 3 atoms of oxygen

= 4 * 12 + 8*1 + 3 * 15.9 (replacing with atomic mass value from periodic table)

= 4*12 + 8 + 3*16 (round off value of oxygen and then multiplying and adding) * multiply

= 48+ 8+ 48

=104 amu (Answer)