How many ml of 95% of ethyl alcohol should be added to sterile water for injection to make 1/2 liter of a 40% ethyl alcohol solution?

V = 210.5  mL

Explanation:

∴ C1 = 0.95

∴ C2 = 0.40

∴ V2 = 0.500 L

⇒ V1 = ((0.50)(0.40))/(0.95)

⇒ V1 = 0.2105 L

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.