Empirical formula The empirical formula of a compound may be defined as the formula which gives the simplest whole number ratio of atoms of the various elements present in the molecule of the compound. sixHseveralO6), is CH2O which shows that C, H, and O are present in the simplest ratio of 1 : 2 : 1. Rules for writing the empirical formula The empirical formula is determined by the following steps :
- Split the fresh percentage of each points by their nuclear bulk. Thus giving the relative amount of moles of numerous points introduce on material.
- Split new quotients gotten in the above step by minuscule of them so as to get a straightforward ratio away from moles of numerous factors.
- Multiply the latest numbers, so acquired of the the ideal integer, if required, so you can obtain whole count proportion.
- Ultimately write down the newest symbols of the numerous factors front side from the side and put the aforementioned wide variety while the subscripts on the straight down right hand area of every symbol. This may depict the fresh empirical formula of your own compound.
Example: A compound, toward investigation, gave the following constitution : Na = cuatrostep three.4%, C = 11.3%, O = forty five.3%. Calculate its empirical algorithm [Nuclear masses = Na = 23, C = 12, O = 16] Solution:
Determination molecular formula : Molecular formula = Empirical formula ? n n = \(\frac < Molecular\quad> < Empirical\quad>\) Example 1: What is the simplest formula of the compound which has the following percentage composition : Carbon 80%, Hydrogen 20%, If the molecular mass is 30, calculate its molecular formula. Solution: Calculation of empirical formula :
? Empirical formula is CH3. Calculation of molecular formula : Empirical formula mass = 12 ? 1 + 1 ? 3 = 15 n = \(\frac < Molecular\quad> < Empirical\quad>=\frac < 30> < 15>\) = 2 Molecular formula = Empirical formula ? 2 = CH3 ? 2 = C2H6.
Example 2: On heating a sample of CaC, volume of CO2 evolved at NTP is 112 cc. Calculate (i) Weight of CO2 produced (ii) Weight of CaC taken (iii) Weight of CaO remaining Solution: eris mobile (i) Mole of CO2 produced \(\frac < 112> < 22400>=\frac < 1> < 200>\) mole mass of CO2 = \(\frac < 1> < 200>\times 44\) = 0.22 gm (ii) CaC > CaO + CO2(1/200 mole) mole of CaC = \(\frac < 1> < 200>\) mole ? mass of CaC = \(\frac < 1> < 200>\times 100\) = 0.5 gm (iii) mole of CaO produced = \(\frac < 1> < 200>\) mole mass of CaO = \(\frac < 1> < 200>\times 56\) = 0.28 gm * Interesting by we can apply Conversation of mass or wt. of CaO = wt. of CaC taken – wt. of CO2 produced = 0.5 – 0.22 = 0.28 gm
Example 3: If all iron present in 1.6 gm Fe2 is converted in form of FeSO4. (NH4)2SO4.6H2O after series of reaction. Calculate mass of product obtained. Solution: If all iron will be converted then no. of mole atoms of Fe in reactant product will be same. ? Mole of Fe2 = \(\frac < 1.6> < 160>=\frac < 1> < 100>\) mole atoms of Fe = 2 ? \(\frac < 1> < 100>=\frac < 1> < 50>\) mole of FeSO4. (NH4)2SO4.6H2O will be same as mole atoms of Fe because one atom of Fe is present in one molecule. ? Mole of FeSO4.(NH4)2.SO4.6H2 = \(\frac < 1> < 50>\times 342\) = 7.84 gm.