Answer:
To find the number of molecules first find the number of moles.
number of moles (n) = mass / molar mass (M)
then use the formula
N = n × L
where n = number of moles
N = number of entities
L = Avogadro's constant = 6.02 × 10^23entities to find the number of molecules
A. 4.9 g H2O
m = 4.9g
M = (2*1)+(16×1) = 2 + 16 = 18g/mol
n = 4.9/18 = 0.272mol
N = 0.272 × 6.02 × 10^23
= 1.6374*10^23 molecules of H2O
B. 54.4g of N2
m = 54.4g
M(N2) = 14×2 = 28g/mol
n = 54.4/28 = 1.942mol
N = 1.942 * 6.02*10^23
= 1.1690*10^24 molecules of N2
C. 89 g CCI4
m = 89g
M(CCl4) = 12 + (35.5 × 4) = 154g/mol
n = 89/154 = 0.577mol
N = 0.577 × 6.02 × 10^23
= 3.473*10^23 molecules of CCl4
D. 11 g C6H12O6
m = 11g
M(C6H12O6) = (12×6)+(12×1)+(16×6) =
180g/mol
n = 11/180 = 0.0611mol
N = 0.0611 × 6.02×10^23
= 3.678*10^22 molecules of C6H12O6
Hope this helps
