What is the volume of the solution produced when enough water is added to 42.0 g of mgcl2 ⋅ 6h2o to yield a solution that has a cl- ion concentration of 0.500m?

827 mL

Explanation:

To answer this question we use the definition of Molarity:

Molarity = mol / L

[Cl⁻] = mol Cl⁻ / L

Now we calculate the moles of Cl⁻ present in 42.0 g of MgCl₂⋅6H₂O:

Molar mass of MgCl₂⋅6H₂O = 24.3 + 2*35.45 + 6*18 = 203.2 g/mol

moles of Cl⁻ = 42.0 g MgCl₂⋅6H₂O ÷ 203.2 g/mol * = 0.4134 mol Cl⁻

Finally we use the definition of molarity to calculate the volume:

0.500 M = 0.4134 mol Cl⁻ / xL

xL = 0.827 L =  827 mL

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.