If 14.23 mL of 0.203 M NaOH is required to neutralize .269 g of a monoprotic unknown acid, what is the molecular weight of the unknown acid?
NaOH + HA --> NaA + H2O
mols NaOH = M x L = ?
mols HA = same since the ratio of acid to base is 1:1 (look at the coefficients)
mols HA = grams/molecular weight. You know mols HA and grams HA, solve for molecular weight.
To find the molecular weight of the unknown acid, we need to use the given information about the volume and concentration of NaOH used to neutralize the acid, and the mass of the acid itself.
Here are the steps to calculate the molecular weight of the unknown acid:
Step 1: Convert the volume of NaOH used to liters:
14.23 mL = 14.23/1000 L = 0.01423 L
Step 2: Calculate the number of moles of NaOH:
0.203 M means 0.203 moles of NaOH per 1 L of solution.
So, the number of moles of NaOH used can be calculated as follows:
moles of NaOH = concentration × volume
moles of NaOH = 0.203 mol/L × 0.01423 L = 0.00289969 mol
Step 3: Calculate the number of moles of unknown acid (using the balanced equation):
Assuming a 1:1 molar ratio between NaOH and the unknown acid, the number of moles of the unknown acid is equal to the number of moles of NaOH.
moles of unknown acid = 0.00289969 mol
Step 4: Calculate the mass of the unknown acid:
mass of unknown acid = moles × molar mass
mass of unknown acid = 0.00289969 mol × molar mass
Step 5: Convert the mass of the unknown acid to grams:
The molar mass is typically expressed in grams per mole.
mass of unknown acid = 0.00289969 mol × (molar mass in g/mol)
Given that the mass of the unknown acid is 0.269 g, we can set up an equation:
0.269 g = 0.00289969 mol × (molar mass in g/mol)
Step 6: Solve the equation for the molar mass of the unknown acid:
molar mass in g/mol = 0.269 g / 0.00288969 mol
molar mass = 93.038 g/mol
Therefore, the molecular weight of the unknown acid is 93.038 g/mol.
To calculate the molecular weight of the unknown acid, we need to use the concept of stoichiometry and the equation:
NaOH + Unknown acid → NaX + H2O
From the given information, we can see that:
- Volume of NaOH used: 14.23 mL
- Concentration of NaOH: 0.203 M
- Mass of the unknown acid: 0.269 g
First, let's calculate the number of moles of NaOH used:
Moles of NaOH = Volume of NaOH (in mL) × Concentration of NaOH (in M)
= 14.23 mL × 0.203 M
= 2.8951 mmol (millimoles)
Next, we need to determine the moles of the unknown acid. Since NaOH and the unknown acid react in a 1:1 ratio, the moles of the unknown acid would be equal to the moles of NaOH used:
Moles of unknown acid = Moles of NaOH
= 2.8951 mmol
Now, we can calculate the molecular weight of the unknown acid using the equation:
Molecular weight = Mass of unknown acid (in g) / Moles of unknown acid
Molecular weight = 0.269 g / 2.8951 mmol
To perform this calculation, we need to convert the mass of the unknown acid from grams to milligrams:
Molecular weight = 269 mg / 2.8951 mmol
Finally, by dividing the mass (in mg) by the moles (in mmol), we can determine the molecular weight of the unknown acid:
Molecular weight ≈ 93.01 g/mol
Therefore, the molecular weight of the unknown acid is approximately 93.01 g/mol.