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**1. The problem statement, all variables and given/known data**

A. When current flows in an ionic solution, both negative and positive ions are charge carriers. In the dilute limit, the resistivity of the solution is inversely proportional to the concentration. For example, the resistivity of salt water solution at 25 °C is

ρ = 8.0645/[NaCl] Ω·cm·mol/L,

where [NaCl] is the concentration of salt in the water, in moles per litre. Calculate the resistance of a cylinder of salt water (in a plastic tube) with radius r = 1.30 cm, length L = 13.80 cm, and [NaCl] = 0.29 mol/L.

B. If a potential difference of V = 69 V (alternating current) is applied, what will the current be?

C. For the situation described, with a current I flowing through the water, what is the drift speed of Na+ ions while the current flows?

**2. Relevant equations**

R=ρ*(L/A)

V=IR

Area of a circle= pi*r

^{2}

I=n*q*v

_{d}*A, where n is the number of charge carriers per unit volume, q is the charge on the charge carriers, v

_{d}is the drift velocity, and A is the cross-sectional area.

**3. The attempt at a solution**

For A. Simply using the formula, I get 72.3 Ohms

For B. Again, via formula use, I get .955 Amperes.

For C. I have no idea what to use for n. I would be .955, q I presume would be 1.602*10

^{-19}, A would be the pi*(1.30/100)

^{2}(since I presume my units would require the area to be given in m^2?)

I tried using the given molarity of 0.29 mol/L=0.29mol/m^3, and multplying that by Avegadros number (6.02*10

^{23}) to get the number of ions per unit volume, but that didn't seem to give me the correct answer.

Anything I'm missing here, or perhaps theres another formula I should be using to get at v

_{d}?