Question

what is mole concept?calculate the number of molecules in 45g of water.

Answer 1

mole concept includes the study of amounts of gases,compounds.Its a wide field.

number of molecules in 45 gms of water.

number of moles in 45 gms of water=45/18
number of molecules in 1 mole of water=3Na
so number of molecules in 45 gms of water(45/18 moles of water)=(45/18)*3Na=(45/6)*Na=(15/2)Na.
done.
let me knw if u have any doubt.

Answer 2

Hello!  

The number of mol or quantity of matter is the quantity of particles called atoms or molecules of a substance.  

By the Law of Avogrado we know that for each mole of substance, we have 6.022*10²³ molecules.  

We have the following data:  

n1 (mol number) = ?

m1 (mass) = 45 g

MM (molar mass of water) = 18 g / mol  

Let's find the number of moles, let's see:

$n_1 = \dfrac{m_1\:(g)}{MM\:(g/mol)}$

$n_1 = \dfrac{45\:\diagup\!\!\!\!\!g}{18\:\diagup\!\!\!\!\!g/mol}$

$\boxed{n_1 = 2.5\:mol}$

Now, let us make the relation with the Law of Avogrado, let us see:

1 mol ----------------- 6.022*10²³ molecules

2.5 mol ------------- y

$\dfrac{1}{2.5} = \dfrac{6.022*10^{23}}{y}$

Product of extremes equals product of means:

$1*y = 2.5*6.022*10^{23}$

$y = 15.055*10^{23}$

$\boxed{\boxed{y = 1.5055*10^{24}\:molecules}}\end{array}}\qquad\checkmark$

__________________________

I Hope this helps, greetings ... Dexteright02! =)