Question

the largest number of molecules is in:
a)36 gm H2o
b)28 gm CO
c)46 gm C2H2OH
d)54 gm NO5

Answer 1

The largest number of molecules is in:

a) 36 gm H₂O

b) 28 gm CO

c) 46 gm C₂H₂OH

d) 54 gm NO₅

Solution:

1) Find the amount of compound by the following formula:

$$n = \frac{m}{M}$$

$n - \text{Amount of substance}$

$m - \text{mass of the substance}$

$M - \text{the molar mass of the substance}$

$$n(H_2O) = \frac{36g}{18g/\text{mole}} = 2\text{mole}$$ $$n(CO) = \frac{28g}{28g/\text{mole}} = 1\text{mole}$$ $$n(C_2H_2OH) = \frac{46g}{43g/\text{mole}} = 1,07\text{mole}$$ $$n(NO_5) = \frac{54g}{94g/\text{mole}} = 0,57\text{mole}$$

2) Knowing this value as the amount of compound, get the number of molecules in it. For this amount of material, measured in moles, multiply by the Avogadro constant ($N_A = 6,022 \cdot 10^{23}$)

$$N = n * N_A$$

So,

$$N(H_2O) = 2 * 6,02 * 10^{23} = 12,04 * 10^{23}$$ $$N(CO) = 1 * 6,02 * 10^{23} = 6,02 * 10^{23}$$ $$N(C_2H_2OH) = 1,07 * 6,02 * 10^{23} = 6,44 * 10^{23}$$ $$N(NO_5) = 0,57 * 6,02 * 10^{23} = 3,43 * 10^{23}$$

Answer: The largest number of molecules is in 36 g of water ($H_2O$)