Question

How many grams of naoh are needed to give a ph of 11.5 in a 14.5 l tank of water?

Answer 1

To calculate the grams of NaOH needed to give a pH of 11.5 in a 14.5 L tank of water, you need to determine the molarity of NaOH required and then use the molarity formula to find the moles of NaOH. Finally, convert the moles of NaOH to grams using the molar mass of NaOH.

Step-by-step explanation:

To determine the grams of NaOH needed to give a pH of 11.5 in a 14.5 L tank of water, you need to calculate the molarity of NaOH required.

The pH scale is logarithmic, meaning that each unit change in pH represents a tenfold change in acidity or basicity. So, to go from a pH of 14 to 11.5, you are moving 2.5 units towards basicity.

Now, to calculate the grams of NaOH needed, you need to use the molarity formula:

Molarity (M) = moles of solute / volume of solution (L)

Since we know the volume of the tank (14.5 L) and the desired pH change (2.5), we can calculate the molarity of NaOH needed:

Molarity (M) = 10^(-pH) = 10^(-11.5) = 3.16 x 10^(-12) M

Now, to calculate the moles of NaOH needed:

Moles of solute = Molarity x volume of solution (L) = (3.16 x 10^(-12) M) * (14.5 L)

Remember that 1 mole of NaOH is equivalent to its molar mass in grams, which is approximately 40 g/mol. Therefore, the grams of NaOH needed is:

Grams of NaOH = Moles of NaOH x molar mass of NaOH = (3.16 x 10^(-12) M) * (14.5 L) * (40 g/mol)

After performing the calculations, the answer would be the final value in grams of NaOH.

Answer 2

1.84 grams of NaOH are needed to give a pH of 11.5 in a 14.5 L tank of water.

To solve this problem

As stated: Ideal pH is 11.5

Water volume = 14.5 L; water dissociation constant = 14.00 pKw

To determine: NaOH mass (g)

Firstly, let calculate the pOH

pOH = 14.00 - 11.5 = 2.50

Secondly, let calculate the concentration of OH⁻ ions

[OH⁻] =
`10^-^p^O^H` =
`10^-^2^.^5^0`= 3.16 × 10⁻⁵ M

Now, let calculate the moles of OH⁻ ions

moles of OH⁻ = [OH⁻] × volume of water = 3.16 × 10⁻⁵ M × 14.5 L = 4.6 × 10⁻⁴ mol

Let, calculate the moles of NaOH

Since NaOH dissociates completely in water, the moles of OH⁻ ions are equal to the moles of NaOH.

moles of NaOH = moles of OH⁻ = 4.6 × 10⁻⁴ mol

Finally, let calculate the mass of NaOH

mass of NaOH = moles of NaOH × molar mass of NaOH = 4.6 × 10⁻⁴ mol × 40.00 g/mol = 1.84 g

So, 1.84 grams of NaOH are needed to give a pH of 11.5 in a 14.5 L tank of water.