Calculation of Molecular Weight of the Unknown Acid: Since the unknown acid is monoprotic, we can assume that the moles of base = moles of acid at the equivalence point: 0.0494 mole NaOH/L * 0.00570 L = 2.81 x 10-4mole NaOH = 2.81 x 10-4mole acid
How do you find the equivalent mass of an unknown acid?
From your titration data you will determine the number of moles of acid in the sample. From this and the mass of the acid in the sample you will determine the equivalent mass of the unknown acid. In both parts of this experiment you will perform at least three titrations to ensure the precision of your results.
How to weigh the unknown solid acid by difference?
To weigh the unknown solid acid by difference carefully remove the cap from the sample vial and set it aside. Weigh your sample vial and its contents on the analytical balance. Record this mass on your data sheet. Now transfer a small amount of the solid acid from the vial directly into your 250-mL Erlenmeyer flask.
How do you find the molar mass from the equivalent mass?
In all cases the molar mass and the equivalent mass are related by simple equations, but in order to find the molar mass from the equivalent mass we need to know the molecular formula of the acid.
What is the mass of solid acid used in each trial?
The mass of solid acid you will require for each trial depends on the particular unknown acid sample used and is given on the label of each sample. This should be a value between 0.1 and 0.5 grams. We will now use a technique called weighing by difference to measure this mass of solid acid used in each trial.
How do you find the equivalent weight of an unknown acid?
For an acid like HCl, which has only one ionizable hydrogen, the equivalent weight is the same as the molar mass….Overview.AcidMolar MassEquivalent WeightHCl36.5 g36.5 gH2SO498.0 g98.0g/2 = 49.0 gH3PO498.0 g98.0g/3 = 32.7 g2 more rows
How do you find the unknown acid in a titration?
Your unknown solid is an acid. You will dissolve it in water, add some phenolphthalein indicator and then titrate to the end point with your standard NaOH solution. The unknown acid is monoprotic; it has only one acidic hydrogen per molecule.
How do you find the equivalent weight of a titration?
You will use the midpoint of the steepest portion of your titration curve to determine the volume at the equivalence point, and from the normality of your NaOH, calculate the equivalent weight of your acid. You can then divide the volume at the equivalence point by 2 to determine the dissociation constant of your acid.
How do you find the equivalent of an acid?
It is calculated by dividing the molecular weight of solute by the number of equivalents per mole of solute (Equation 2). For acids, the number of equivalents per mole is the number of H+ ions contributed by the acid per mole of acid.
How do you identify an unknown acid?
List of Possible AcidsCalibrate pH probes using buffer solutions.Dissolve 0.1g unknown acid in 10mL DI water in a beaker.Fill buret with NaOH (molarity = 0.1198M)Add 2 drops of phenolphthalein indicator.Place pH probe in acid solution.Start dropping NaOH into acid solution, stop every 0.5mL NaOH and record pH.More items…
How do you determine the identity of an unknown acid?
The melting point of the solid acid will be found using a Meltemp. From the experimental values of molar mass (as derived from the equivalence point), pKa, and melting point, the identity of the unknown acid will be chosen from a list of possible weak acids.
What is the formula of equivalent weight?
Equivalent Weight = Molecular weight/ Valency Also, read: Chemical Reaction.
How do you find the equivalent weight of HCl?
Solution : equivalent mass of an acid
`=(“Molar mass of the acid”)/(“Basicity of the acid “)`
Equivalent mass of `HCI=(36.5)/(1)`
`=36.5` .
How do you find the equivalent weight of h2so4?
We will solve this problem by using the general formula and the atomic masses of elements from the periodic table.Molecular formula of Sulphuric acid is H2SO4Atomic mass of Hydrogen (H) = 1u.Atomic mass of Sulphur (S) = 32u.Atomic mass of Oxygen (O) = 16u.
What is the equivalent weight of an acid?
The equivalent weight of an acid or base for neutralization reactions or of any other compound that acts by double decomposition is the quantity of the compound that will furnish or react with or be equivalent to 1.008 g of hydrogen ion or 17.0074 g of hydroxide ion—e.g., hydrochloric acid (HCl), 36.461 g; sulfuric …
What is meant by equivalent weight of an acid?
For acid–base reactions, the equivalent weight of an acid or base is the mass which supplies or reacts with one mole of hydrogen cations (H + ). For redox reactions, the equivalent weight of each reactant supplies or reacts with one mole of electrons (e−) in a redox reaction.
How do you find the equivalent weight of NaOH?
To begin, we must determine the molecular weight of sodium hydroxide (NaOH). Sodium has a molecular weight of 23 g/mol, oxygen has a molecular weight of 16 g/mol, and hydrogen has a molecular weight of 1 g/mol. Now, the molecular weight of sodium hydroxide will be: Mol. wt = 23 + 16 + 1 = 40 g/mol.
How do you calculate equivalent?
To calculate the equivalent mass of a base, simply divide the molar mass of the base by the number of hydroxyl groups. Take, for example, calcium hydroxide Ca(OH)₂. A few simple calculations yield an equivalent of 37g/mol. To find the equivalent of an acid, divide the acid’s molar mass by the number of protons.
What is equivalent weight of NaOH?
Hence, the equivalent weight of NaOH is 40g/mol.
What is an equivalence point in a titration?
Equivalence point: point in titration at which the amount of titrant added is just enough to completely neutralize the analyte solution. At the equivalence point in an acid-base titration, moles of base = moles of acid and the solution only contains salt and water.
What is equivalent weight of base?
The equivalent weight of base : is the weight of compound that contains one equivalent of hydroxide ion (OH-) . Formula for calculating equivalent weight of base = molecular weight / acidity of base. For Ca(OH)2 : acidity is two as it can donate two OH- ions. It’s equivalent weight is = molecular weight /2.
What is the mass of acid?
The mass of solid acid you will require for each trial depends on the particular unknown acid sample used and is given on the label of each sample. This should be a value between 0.1 and 0.5 grams.
How much NaOH to add to 500 ml?
Using the small graduated cylinder, measure approximately 8 mL of 6-M NaOH solution into the 500-mL flask. Using your 600-mL beaker, measure approximately 400 mL of deionized water and add this to the 8 mL of NaOH in your flask. (These measurements do not need to be exact because you will standardize this solution later). Stopper and label this solution, “sodium hydroxide solution”. Swirl your sodium hydroxide solution well before proceeding to be certain it is completely mixed. Leave the stopper in place when you are not pouring the solution into another container.
How to clean a 250 ml Erlenmeyer flask?
Clean and rinse a 250-mL Erlenmeyer flask using deionized water. This flask does not need to be dried.
What is the molarity of NaOH?
They standardized their NaOH and found its molarity to be 0.1098 M.
How many drops of phenolphthalein indicator to HCl?
Add 2 or 3 drops of phenolphthalein indicator to the HCl solution in the 250-mL Erlenmeyer flask.
What is titration in chemistry?
To determine the equivalent mass of an unknown acid. Titrations are used extensively in analytical chemistry. Some applications of titrations include quality control in the food, cosmetics, beverages, and pharmaceutical industries; quantitative determination of chemical concentrations in environmental samples; and the measurement …
How to determine if a titration is a proper endpoint?
A proper endpoint in a titration is reached when a single drop of titrant causes the indicator to change color and the color persists while swirling the solution for at least 30 seconds. If you are unsure whether only a single drop of titrant was dispensed, then you should discard and repeat the trial you are performing (or in some cases you may perform a back titration). The indicator shade being light or dark is not sufficient to determine if a proper endpoint has been reached; some trials may have a darker color than others because the titration curve is very steep in the region of the endpoint. The only accurate determination that the proper endpoint has been reached is if you are certain that only a single drop was required to reach the endpoint signaled by the indicator color change. Any uncertain trials should be discarded.