What is 0.000345 expressed in scientific notation? 3.45 × 102 3.45 × 104 3.45 × 10–2 3.45 × 10–4

Hello you probably have the answer by now. But I just want to help others to know what it is. Just in case they are stuck.

I just took the quiz on e2020 and it is 3.45 × 10^–4. Or letter D or basically last one. Which ever is easier for you but yes those all are the same and the answer.

D

Explanation:

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.