Question

When 90 gm of water is mixed with 300 gm of acetic acid. The total number of moles will be
A . 5
B . 15
C . 10
D . 20

Answer 1

Hint: his question requires the use of the idea of "moles." The amount of material present is referred to as a "mole." The molar mass of the substance can be used to convert between moles and grams. The Avogadro number is the molecular weight in grams for a molecule.

Complete answer:First, let's talk about the Avogadro number and the idea of moles. The term "Avogadro's number" is used to describe how many elementary particles, such as molecules, atoms, compounds, etc., there are in every mole of a substance. It is commonly denoted by the sign NA.
The quantity of units in one mole of any material is also referred to as "Avogadro's number" or "Avogadro's constant." It has a value of 6.023×10^23.
Another property of Avogadro's number is that the mass of a mole of a substance is equal to its molecular weight. Additionally, the mass of an element is equal to its gram atomic mass and the mass of a compound is equal to its molecular mass in grammes.\[Number\text{ }of\text{ }moles=\dfrac{given\text{ }mass}{molar\text{ }mass}\]

The molecular mass of water=18 and that of acetic acid=60
The total number of moles = number of moles of water + number of moles of acetic acid
$n=\dfrac{{{w}_{1}}}{{{m}_{1}}}+\dfrac{{{w}_{2}}}{{{m}_{2}}}=\dfrac{90}{18}+\dfrac{300}{60}=10$
Therefore, the total number of moles=10

The correct answer is C.

Note:This number, 6.023×10^23 (Avogadro’s constant) is actually defined based on the number of atoms present in 12g of 12C isotope of Carbon. Where 12gm is the molar mass of 12C or in other words the mass of 1 mole or 6.023×10^23 atoms of the 12C isotope of Carbon.