A volume of 12.47 mL of 0.1080 M NaOH solution was used to titrate a 0.583 g sample of unknown containing K2HPO4.
What is the percent by mass of K2HPO4 in the unknown?
In this problem what mass of sample in grams would be needed to deliver about 23.40 mL in the next trial?
In the second trial above, exactly 1.082 g was transferred into a flask to be titrated. If the initial buret reading is 0.10 mL, predict what the final buret reading be.
K2HPO4 + NaOH ==> K2NaPO4 + H2O
mols NaOH = M x L = ?
Using the coefficients in the balanced equation convert mols NaOH to mols K2HPO4.
Now grams K2HPO4 = mols x molar mass and
% K2HPO4 = (grams K2HPO4/mass sample)*100 = ?
For #2, plug in 0.1080 for M and 0.02340 for L and solve for mols, then use the next formula I wrote to calculate grams (g = mols x molar mass).
To find the percent by mass of K2HPO4 in the unknown, we first need to calculate the number of moles of NaOH that were used to react with the K2HPO4. Then, we can use stoichiometry to calculate the number of moles of K2HPO4 in the unknown. Finally, we can use the molar mass of K2HPO4 to find the percent by mass.
Step 1: Calculate moles of NaOH used
The volume of NaOH solution used is given as 12.47 mL, and the concentration of NaOH is given as 0.1080 M.
moles of NaOH = volume of NaOH solution (L) * concentration of NaOH (mol/L)
= 0.01247 L * 0.1080 mol/L
Step 2: Calculate moles of K2HPO4
From the balanced chemical equation between NaOH and K2HPO4, we know that the stoichiometric ratio is 2:1. This means that 2 moles of NaOH react with 1 mole of K2HPO4.
moles of K2HPO4 = (moles of NaOH) / 2
Step 3: Calculate the mass of K2HPO4
The molar mass of K2HPO4 can be found by summing the atomic masses of all the elements in the compound.
mass of K2HPO4 = moles of K2HPO4 * molar mass of K2HPO4
Finally, to find the percent by mass of K2HPO4 in the unknown, we divide the mass of K2HPO4 by the mass of the unknown sample and multiply by 100.
percent by mass = (mass of K2HPO4 / mass of unknown) * 100
Now, let's move on to the next questions:
In the second question, we are given the volume that needs to be delivered in the next trial, which is 23.40 mL. We can use the concentration of NaOH solution to calculate the moles of NaOH needed. Then, we can apply stoichiometry to determine the moles of the unknown sample required.
moles of NaOH = volume of NaOH solution (L) * concentration of NaOH (mol/L)
moles of unknown = moles of NaOH * (1 mole of unknown / 2 moles of NaOH)
Finally, to find the mass of the sample needed, we multiply the moles of the unknown sample by its molar mass.
mass of sample = moles of unknown * molar mass of unknown
In the third question, we are given the mass of the sample transferred into the flask (1.082 g). We also know the initial buret reading (0.10 mL). To predict the final buret reading, we need to calculate the number of moles of NaOH that reacted with the sample and convert it to volume using the concentration of NaOH.
moles of NaOH reacted = (mass of sample / molar mass of sample) * (1 mole of NaOH / 1 mole of sample)
volume of NaOH reacted = moles of NaOH reacted / concentration of NaOH (mol/L)
Finally, we subtract the volume of NaOH reacted from the initial buret reading to get the predicted final buret reading.