Question 35The percentage composition of sodium phosphate as determined by analysis is 42.1% sodium, 18.9% phosphorus and 39% oxygen. Find the empirical formula of the compound?

Question

Accepted Answer

Element% compositionAt. wt.Relative no. of atomsSimplest ratiosodium42.12342.123\dfrac{42.1}{23}2342.1​ = 1.831.830.609\dfrac{1.83}{0.609}0.6091.83​ = 3phosphorus18.93118.931\dfrac{18.9}{31}3118.9​ = 0.6090.6090.609\dfrac{0.609}{0.609}0.6090.609​ = 1oxygen39163916\dfrac{39}{16}1639​ = 2.432.430.609\dfrac{2.43}{0.609}0.6092.43​ = 4Simplest ratio of whole numbers = Na : P : O = 3 : 1 : 4Hence, empirical formula is Na3PO4

Element	% composition	At. wt.	Relative no. of atoms	Simplest ratio
sodium	42.1	23	$\dfrac{42.1}{23}$ = 1.83	$\dfrac{1.83}{0.609}$ = 3
phosphorus	18.9	31	$\dfrac{18.9}{31}$ = 0.609	$\dfrac{0.609}{0.609}$ = 1
oxygen	39	16	$\dfrac{39}{16}$ = 2.43	$\dfrac{2.43}{0.609}$ = 4

Mole Concept & Stoichiometry Miscellaneous Exercises — Question 36

Question 35