Question

Calculate the mass percent composition of each of the following @ Mg F2, magnesium fluoride 16 C4 H ₂ O4, erythrose, a carbohydrate

Answer 1

To calculate mass percent composition of each of the following:

Formula to be used: (Mass of element / Total mass of compound) $\times$ 100%

1. MgF2

Atomic mass of Mg: 24.305 amu

Atomic mass of F: 18.9984 amu

Total mass of magnesium flouride: 24(1) + 18(2) = 62.3018

Mass percent composition of Mg in MgF2: (Mass of Mg / Total mass of MgF2) $\times$ 100%

= (24.305 / 62.3018) $\times$ 100% = 39.011%

Mass percent composition of F in MgF2: (Mass of F$\times$2 / Total mass of MgF2) $\times$ 100%

= (18.9984 $\times$ 2 / 62.3018) $\times$ 100% = 60.98%

Mg = 39.011%, F = 60.98%

2. C4H8O4 (erythrose)

Atomic mass of Carbon: 12 amu

Atomic mass of Hydrogen: 1 amu

Atomic mass of Oxygen: 16 amu

Total mass of erythrose: Mass of C(4)+Mass of H(8)+mass of O(4) = 12(4)+1(8)+16(4) = 120

Mass percent composition of Carbon in C4H8O4: (Mass of C$\times$4 / Total mass of C4H8O4 ) $\times$ 100%

= (12$\times$4 / 120) $\times$ 100% = (48 / 120) $\times$ 100% = 40%

Mass percent composition of hydrogen in C4H8O4: (Mass of H$\times$8 / Total mass of C4H8O4 ) $\times$ 100%

= (1$\times$8 / 120) $\times$ 100% = 6.66%

Mass percent composition of oxygen in C4H8O4: (Mass of O$\times$4 / Total mass of C4H8O4 ) $\times$ 100%

= (16$\times$4 / 120) $\times$ 100% = (64 / 120)$\times$100% = 53.33%

C = 40%, H = 6.66%, O = 53.33%