Answer to Question #204482 in Chemistry for Taylor

Question

1. Questions 8 to 12—convert the following number of moles to number of particles:
2. 2.0 moles of CaCl₂
3. 1.5 moles of copper(II) ions
4. 0.01 moles of H₂O
5. 5.0 moles of gold atoms
6. 0.0025 moles of HCl
7. What is the mass of 1 mole of Mg atoms?
8. What is the molar mass of aluminum?
9. What is the mass of 1 mole of oxygen atoms?
10. What is the mass of 1 mole of oxygen molecules, O₂?
11. Calculate the molar mass of NaOH.
12. What is the mass of 1.0 mole of CaCl₂?
13. Calculate the molar mass of Cu(NO₃)₂.
14. Calculate the molar mass of Al₂(SO₄)₃.

Answer 1

Solution:

One mole of any substance contains 6.022×10²³ particles.

Thus:

2)

Number of CaCl₂ molecules = (2.0 mol CaCl₂) × (6.022×10²³ molecules / 1 mol) = 1.20×10²⁴ molecules

Number of CaCl₂ molecules = 1.20×10²⁴ CaCl₂ molecules

3)

Number of Cu²⁺ ions = (1.5 mol Cu²⁺) × (6.022×10²³ ions / 1 mol) = 9.03×10²³ Cu²⁺ ions

Number of Cu²⁺ ions = 9.03×10²³ Cu²⁺ ions

4)

Number of H₂O molecules = (0.01 mol H₂O) × (6.022×10²³ molecules / 1 mol) = 6.02×10²¹ molecules

Number of H₂O molecules = 6.02×10²¹ H₂O molecules

5)

Number of Au atoms = (5.0 mol Au) × (6.022×10²³ atoms / 1 mol) = 3.01×10²⁴ Au atoms

Number of Au atoms = 3.01×10²⁴ Au atoms

6)

Number of HCl molecules = (0.0025 mol HCl) × (6.022×10²³ molecules / 1 mol) = 1.51×10²¹ molecules

Number of HCl molecules = 1.51×10²¹ HCl molecules

7)

The molar mass of Mg is 24.305 g/mol.

So, 1 mol of Mg atoms has a mass: (1 mol Mg) × (24.305 g Mg / 1 mol Mg) = 24.305 g Mg

8)

The molar mass of Al is 26.98 g/mol.

9)

The molar mass of O is 15.999 g/mol.

So, 1 mol of oxygen atoms has a mass: (1 mol O) × (15.999 g O / 1 mol O) = 15.999 g O atoms

10)

The molar mass of O₂ is 31.998 g/mol.

So, 1 mol of O₂ molecules has a mass: (1 mol O₂) × (31.998 g O₂ / 1 mol O₂) = 31.998 g O₂ molecules

11)

M(NaOH) = Ar(Na) + Ar(O) + Ar(H) = 22.989 + 15.999 + 1.008 = 39.996 (g/mol).

The molar mass of NaOH is 39.996 g/mol.

12)

M(CaCl₂) = Ar(Ca) + 2×Ar(Cl) = 40.078 + 2×35.453 = 110.984 (g/mol).

The molar mass of CaCl₂ is 110.984 g/mol.

So, 1 mol of CaCl₂ has a mass: (1 mol CaCl₂) × (110.984 g CaCl₂ / 1 mol CaCl₂) = 110.984 g CaCl₂

13)

M(Cu(NO₃)₂) = Ar(Cu) + 2×Ar(N) + 6×Ar(O) = 63.546 + 2×14.007 + 6×15.999 = 187.554 (g/mol).

The molar mass of Cu(NO₃)₂ is 187.554 g/mol.

14)

M(Al₂(SO₄)₃) = 2×Ar(Al) + 3×Ar(S) + 12×Ar(O) = 2×26.98 + 3×32.065 + 12×15.999 = 342.143 (g/mol).

The molar mass of Al₂(SO₄)₃ is 342.143 g/mol.

Answers:

2) 1.20×10²⁴ CaCl₂ molecules;

3) 9.03×10²³ Cu²⁺ ions;

4) 6.02×10²¹ H₂O molecules;

5) 3.01×10²⁴ Au atoms;

6) 1.51×10²¹ HCl molecules;

7) 24.305 g Mg;

8) the molar mass of Al is 26.98 g/mol;

9) 15.999 g O atoms;

10) 31.998 g O₂ molecules;

11) the molar mass of NaOH is 39.996 g/mol;

12) 110.984 g CaCl₂;

13) the molar mass of Cu(NO₃)₂ is 187.554 g/mol;

14) the molar mass of Al₂(SO₄)₃ is 342.143 g/mol.