Question

URGENT!! Chemistry gurus-- I summon thee!

1. A solution is formed by dissolving 83.2 grams of copper II chloride (CuCl2) in 2.5 liters of water. The molar mass of CuCl2 is 134.45 g/mol.


What is the molarity of the solution?


I think its .25 but im not too sure


2. Study the reaction.

2CH4 + 2O2 → CO2 + 2H2O

If 7.4 moles of carbon dioxide (CO2) form at the end of the reaction, how many moles of methane (CH4) and oxygen gas (O2) entered the reaction?


answering both of these questions would be awesome but one is enough :)

Answer 1

1. Molarity : 0.25 M

2. mol CH₄ = 7.4 moles

mol O₂ = 14.8 moles

Further explanation

1.

Given

83.2 g CuCl2 in 2.5 liters of water

Required

the molarity

Solution

Molarity : mol solute per liter of solution(not per liter of solvent)

• mol solute

mol solute = mol CuCl₂

mol CuCl₂ = mass : MW CuCl₂

mol CuCl₂ = 83.2 : 134.45

mol CuCl₂ = 0.619

• Molarity

Molarity(M) = mol : V

Assume density CuCl₂ = 3.39 g/cm³

volume CuCl₂ = 8.32 g : 3.39 g/cm³ = 2.45 cm³=2.45 x 10⁻³ L

With this small volume value of CuCl₂, the volume of the solute is sometimes neglected in calculating molarity

volume of solution = 2.5 L + 2.45 x 10⁻³ L = 2.50245 L

Molarity(M) = mol : V

M = 0.619 : 2.50245 L = 0.247≈0.25

2.

Given

Reaction

The correct balanced reaction:

CH4 + 2O2 → CO2 + 2H2O

7.4 moles CO2

Required

moles of methane (CH4) and oxygen gas (O2)

Solution

From the equation, mol ratio of CO₂ : CH₄ : O₂ = 1 : 1 : 2

mol CH₄ = mol CO₂ = 7.4 moles

mol O₂ = 2 x mol CO₂ = 2 x 7.4 moles = 14.8 moles