To aid in the prevention of tooth decay, it is recommended that drinking water contains 0.900 ppm fluoride ( a) how many g of f- must be added to a cylindrical water reservoir having a diameter of 3.36x10^2 m and a depth of 21.80 m? b) how many grams of sodium fluoride, naf, contain this much fluoride?

a) 1.740 g of F- must be added to a cylindrical water reservoir

b) Grams of sodium fluoride, NaF, that contain this much fluoride:

3.84 g

Explanation:

Step 1. calculate the volume of the tank:

Volume of cylinder =

,

Here r = radius of the cylinder = d/2

h = depth = 21.80m

= 168 m

Volume =

2.Convert ppm to g/m3 and Solve for mass of F-

Because both ppm and g/m3 are same quantity .

mass of F- required = 1.740 g

3. Apply mole concept to calculate grams of sodium fluoride produced

mass of 1 mole of F2 = 38 g

mass of 1 mole of NaF = 42 g

(from periodic table calculate molar mass)

Here 1 mole of F2 produce = 2 mole of NaF

So,

38 g  of F2 produce = 2 x 42 g of NaF

38 g of F2 produce = 84 g of NaF

1 g of F2 produce = 84/38 g of NaF

1.74 g F2 produce =

1.74 g F2 produce = 3.84 g of NaF

3.84 g of NaF is produced

the answer for sodium is 0.186

the answer for rubidium is 0.251