Calculate the PH of the 0.4g of NaoH in water to give 200ml of solution
Start with the definition:
pH=14-log(concentraiionOH)
but concentration of OH is moles/liters
OH concentration= (.4g/40g/mole)/.2liters
so do the math:
pH=14-log(.05)
which is about 12.5 work it out. Yep, pH is alkaline.
To calculate the pH of a solution of NaOH, we need to know the concentration of NaOH in moles per liter. From the given information, we have 0.4 grams of NaOH and a volume of 200 mL.
Step 1: Convert the given mass of NaOH to moles.
The molar mass of NaOH is calculated by adding the atomic masses of sodium (Na), oxygen (O), and hydrogen (H):
Na = 22.99 g/mol
O = 16.00 g/mol
H = 1.01 g/mol
Molar mass of NaOH = (22.99 g/mol) + (16.00 g/mol) + (1.01 g/mol) = 39.99 g/mol
To convert the mass of NaOH to moles, divide the given mass by the molar mass:
Number of moles = 0.4 g / 39.99 g/mol ≈ 0.010 mol
Step 2: Convert the volume from milliliters to liters.
Given volume = 200 mL
Number of liters = 200 mL / 1000 mL/L = 0.2 L
Step 3: Calculate the molarity (concentration) of the NaOH solution.
Molarity (M) = Number of moles / Number of liters
Molarity of NaOH = 0.010 mol / 0.2 L = 0.05 M
Step 4: Calculate the pOH of the solution using the concentration of NaOH.
pOH = -log10(Molarity)
pOH = -log10(0.05) = 1.30
Step 5: Calculate the pH of the solution using the pOH.
pH + pOH = 14 (at 25°C)
pH = 14 - 1.30 = 12.70
Therefore, the pH of a 0.4 g NaOH solution in water, when diluted to 200 mL, is approximately 12.70.
To calculate the pH of a solution of NaOH, you need to know the concentration of NaOH in moles per liter (M). From there, you can determine the dissociation of NaOH in water to calculate the concentration of OH- ions, which will allow you to calculate the pOH. Finally, you can convert the pOH to pH using the relationship pH = 14 - pOH.
Here are the calculations step by step:
1. Calculate the number of moles (n) of NaOH:
Given mass = 0.4g
Molar mass of NaOH = 22.99(g/mol) + 16(g/mol) + 1.01(g/mol) = 39.997(g/mol) ≈ 40(g/mol)
n = mass / molar mass = 0.4g / 40(g/mol) = 0.01 mol
2. Calculate the concentration (C) of NaOH:
Volume of solution = 200ml = 0.2L
C = n / V = 0.01 mol / 0.2 L = 0.05 M
3. Determine the moles of OH- ions (OH-) produced by NaOH when it dissociates in water:
NaOH dissociates into Na+ and OH- ions in water in a 1:1 ratio. So, the concentration of OH- ions (C(OH-)) will also be 0.05 M.
4. Calculate the pOH:
pOH = -log10(C(OH-))
5. Calculate the pH:
pH = 14 - pOH
Using these calculations, you can find the pH of the NaOH solution.