Molarity is one way of expressing concentration and is equal to the number of moles of the solute per liter of the solution. Therefore,
Molarity = 2.39 mol / L solution
2.39 ( 1.0) = 2.39 mol HF
Hope this answers the question.
I'd say that his comb has a static electricity charge. It can either be negative, or positive. Let's just say it's positive, and the water is negatively charged. This means that it will affect the water flow when the two charges meet. I hope this helps! ~Mia