Question

How many atoms are in 5 grams of H2O?

Answer 1

Hello!

We know that by the Law of Avogrado, for each mole of substance we have 6.02 * 10²³ atoms, if:

The molar mass of water (H2O)

H = 2 * (1u) = 2u

O = 1 * (16u) = 16u

---------------------------

The molar mass of H2O = 2 + 16 = 18 g / mol

If:

1 mol we have 6.02 * 10²³ atoms

1 mole of H2O we have 18 g

Then we have:

18 g ------------- 6.02 * 10²³ atoms

5 g -------------- x

$\dfrac{18}{5} = \dfrac{6.02*10^{23}}{x}$

$18*x = 5*6.02*10^{23}$

$18\:x = 3.01*10^{24}$

$x = \dfrac{3.01*10^{24}}{18}$

$\boxed{\boxed{x \approx 1.672*10^{23}\:atoms}}\end{array}}\qquad\checkmark$

I Hope this helps, greetings ... DexteR! =)

Answer 2

We know that , Oxygen is diatomic

n=mass of sub ÷Molar mass of sub

& Here given 5 gram O2 molecules not atoms

So n= 5÷32=0.1562 moles O2

TotaO2=0.1562×6.022×10^23 O2molecules

TotalO2=0.9409×10^23 O2 molecules

Now one Oxygen molecule correspond to two Oxygen atoms

So no of oxygen atoms(X)

X=2×0.9409×10^23 oxygen atoms

X= 1.881×10^23 Oxygen atoms

Hence 5 gram oxygen containing 1.881×10^23 Oxygen atoms