Answer to Question #201294 in General Chemistry for ARCHIE MEDINA

Question

DIRECTIONS: Solve the following.

1. Determine the number of atoms in 1.75 mol Al

2. Calculate the number of formula units in 25.0 mol NaNO3

3. Given 6.25 mol H O2 determine the number of molecules.

Answer 1

Mole=$\frac{Mass}{Molar mass}$

Molarity= $\frac{Mass of solute}{ volume in liters}$

Molality= $\frac{moles of solute} {volume of solvent in kg}$

These are the common formulas related to moles that are used in chemical calculations. 

1) When aluminum has 1.75 moles, we need to calculate the number of atoms in it. For calculating the number of moles, the value is multiplied by the Avogadro's number.

One mole=6.022×10²³

Number of atoms=$\frac{1.75mol}{1mol}$ ×6.022×10²³atoms

Number of atoms =1.05×10²⁴atoms

2) In sodium nitrate, 25.0 moles are present. To calculate the number of formula units in it, we need to multiply the moles value by Avogadro's number.

One mole=6.022×10²³

Number of formula units =$\frac{25.0mol}{1mol}$ ×6.022×10²³formula units

Number of formula units =1.51×10²⁵formula units

3) In sodium nitrate, 25.0 moles are present. To calculate the number of formula units in it, we need to multiply the moles value by Avogadro's number.

One mole =6.022×10²³

Number of molecules =$\frac{6.25mol}{1mol}$ ×6.022×10²³molecules

Number of molecules =3.76×10²⁴molecules