Answer:
Empirical formula: Na3S4O9
Molecular formula: Na6S8O18
Explanation:
1) To find the empirical formula, which is the simplest whole number ratio of each element that makes up this unknown compound, we first divide the portion of each element by it's respective atomic mass.
Na= 23g/mol, S= 32g/mol, O=16g/mol
Na = 20.2/23 = 0.878mol
S = 37.6/32 = 1.175mol
O = 42.2/16 = 2.638mol
Next, we divide each number of moles by the smallest value (0.878mol)
Na = 0.878/0.878 = 1
S = 1.175/0.878 = 1.34
O = 2.638/0.878 = 3.004
Next, we multiply each decimal fraction by 3 to make it whole no:
Na = 3
S= 4.02 ~ 4
O= 9.012 ~ 9
The simplest ratio between Na, S and O is 3:4:9 hence, the empirical formula is Na3S4O9
2) To get the molecular formula, we use the molecular weight of each element in the empirical ratio, and the overall molar mass of the compound i.e.
Molar mass of compound= 682.8g/mol
molecular weight of Na3S9O4 = (3 x 23g/mol) + (4 x 32 g/mol) + (9 x 16 g/mol)
= 69 + 128 + 144
= 341 g/mol
Hence, (Na3S4O9)n = 682.8g/mol
= (341)n = 682.8
n = 682.8/341
n = 2.002
n~ 2
Hence, molecular formula = (Na3S4O9)2
= Na6S8O18
The empirical and molecular formula are Na₃S₄O₉ and Na₆S₈O₁₈
respectively.
The empirical formula can be gotten by dividing each element by it's
respective atomic mass.
Na= 23g/mol, S= 32g/mol, O=16g/mol
Na = 20.2/23 = 0.878mol
S = 37.6/32 = 1.175mol
O = 42.2/16 = 2.638mol
Then divide each number of moles by the smallest value which in this case is 0.878mol.
Na = 0.878/0.878 = 1
S = 1.175/0.878 = 1.34
O = 2.638/0.878 = 3.004
Next, we multiply each decimal fraction by 3 to make it whole no:
Na = 3
S= 4.02 ~ 4
O= 9.012 ~ 9
The simplest ratio between Na, S and O is 3:4:9 hence, the empirical formula is Na₃S₄O₉
The molecular formula is calculated by multiplying the molecular weight of each element with empirical ratio to get overall molar mass of the compound
Molar mass of compound is given as 682.8g/mol
Molecular weight of Na₃S₉O₄ = (3 x 23g/mol) + (4 x 32 g/mol) + (9 x 16 g/mol)
= 69 + 128 + 144
= 341 g/mol
Hence, (Na3S4O9)n = 682.8g/mol
= (341)n = 682.8
n = 682.8/341
n = 2.002
n~ 2
Hence, molecular formula = (Na₃S₄O₉)²
= Na₆S₈O₁₈
