Calculate the number of moles present in 5.85 g of NaCl.

📘 Number of Moles Calculation

Step 1: Given Data

Mass of NaCl = 5.85 g

We need to calculate the number of moles of NaCl.

Step 2: Calculate Molar Mass of NaCl

Atomic masses:

Na = 23 g mol⁻¹

Cl = 35.5 g mol⁻¹

Therefore:

Molar Mass of NaCl

= 23 + 35.5

= 58.5 g mol⁻¹

🎬 NaCl Molar Mass Animation

Na + Cl → 58.5 g mol⁻¹

NaCl contains one Na and one Cl per formula unit.

Step 3: Use the Mole Formula

The formula for calculating moles is:

Moles = Mass ÷ Molar Mass

Step 4: Substitute the Values

Moles of NaCl

= 5.85 ÷ 58.5

= 0.10 mol

🎬 Calculation Animation

5.85 g NaCl ÷ 58.5 g mol⁻¹ → 0.10 mol

The given mass is divided by the molar mass to obtain the number of moles.

✅ Final Answer

Number of moles of NaCl = 0.10 mol

Therefore, 5.85 g of NaCl contains 0.10 mole of NaCl.

🎯 Quick Formula

n = m / M

n = 5.85 / 58.5

n = 0.10 mol

Calculate the total number of hydrogen and oxygen atoms present in 2 moles of H2O.

📘 Number of Atoms Calculation

Step 1: Understand the formula of water

H₂O

One molecule of H₂O contains:

2 Hydrogen atoms + 1 Oxygen atom

Therefore, one molecule of water contains a total of 3 atoms.

Step 2: Find the number of H₂O molecules

We know that:

1 mole = 6.022 × 10²³ molecules

Therefore, for 2 moles of H₂O:

Number of H₂O molecules

= 2 × 6.022 × 10²³

= 1.2044 × 10²⁴ molecules

🎬 Water Molecule Animation

Each H₂O molecule contains 2 H atoms and 1 O atom.

H H O

H₂O = 2H + 1O

Step 3: Calculate hydrogen atoms

Each H₂O molecule contains 2 hydrogen atoms.

Number of H atoms

= 2 × 1.2044 × 10²⁴

= 2.4088 × 10²⁴ atoms

Step 4: Calculate oxygen atoms

Each H₂O molecule contains 1 oxygen atom.

Number of O atoms

= 1 × 1.2044 × 10²⁴

= 1.2044 × 10²⁴ atoms

Step 5: Calculate total number of atoms

Total atoms

= H atoms + O atoms

= 2.4088 × 10²⁴ + 1.2044 × 10²⁴

= 3.6132 × 10²⁴ atoms

🎬 Final Atom Count

2 mol H₂O → 1.2044 × 10²⁴ H₂O molecules

H H O → 3 atoms per H₂O

✅ Final Answer

Hydrogen atoms
= 2.4088 × 10²⁴

Oxygen atoms
= 1.2044 × 10²⁴

Total atoms
= 3.6132 × 10²⁴ atoms

🎯 Quick Method

Molecules = Moles × N_A

H atoms = Molecules × 2

O atoms = Molecules × 1

N_A = 6.022 × 10²³ mol⁻¹

Calculate the molar mass of H 2 ​ SO 4 ​ .

📘 Molar Mass Calculation

Step 1: Write the molecular formula

H₂SO₄

The formula contains:

• 2 Hydrogen (H) atoms
• 1 Sulphur (S) atom
• 4 Oxygen (O) atoms

Step 2: Write the atomic masses

H = 1 g mol⁻¹

S = 32 g mol⁻¹

O = 16 g mol⁻¹

🎬 Atomic Mass Animation

H H + S + O O O O

Each atom contributes its atomic mass to the total molar mass.

Step 3: Calculate the contribution of each element

Hydrogen:
2 × 1 = 2 g mol⁻¹

Sulphur:
1 × 32 = 32 g mol⁻¹

Oxygen:
4 × 16 = 64 g mol⁻¹

Step 4: Add all contributions

Molar Mass of H₂SO₄

= (2 × 1) + (1 × 32) + (4 × 16)

= 2 + 32 + 64

= 98 g mol⁻¹

🎬 Final Calculation

H₂ + S + O₄ → 2 + 32 + 64 → 98 g mol⁻¹

✅ Final Answer

Molar Mass of H₂SO₄ = 98 g mol⁻¹

Therefore, one mole of H₂SO₄ has a mass of 98 grams.

🎯 Quick Method

Molar Mass = Σ (Number of Atoms × Atomic Mass)

H₂SO₄ = (2×1) + (1×32) + (4×16)

= 98 g mol⁻¹