Question

How many moles of specified particles are present in a sample of each of the following substances if each sample weighs 7.00 g?
a. N2O molecules
b. NO2 molecules
c. P4O10 molecules
d. V atoms

Answer 1

(a) N₂O molecules

RAM of N=14, O=16

RMM = (14 x2) + 16 = 44g/mol

Moles $=\dfrac{mass}{RMM} = \dfrac{7g}{44g/mol}$

= 0.159moles

(b) NO₂ molecules

RMM = 14 + (16 x 2) = 46g/mol

Moles $= \dfrac{7g}{46g/mol} = 0.152 moles$

(c) P₄O₁₀ molecules

RAM of P=31, O=16

RMM = (31 x 4) + (16 x 10) = 284g/mol

Moles $= \dfrac{7g}{284g/mol} = 0.0246 moles$

(d) V atoms

RAM of V = 50.9g/mol

Moles $= \dfrac{7g}{50.9g} = 0.139 moles$