A student actually used 0.847g sample of impure KHP and the endpoint was reached after 19.82 ml of sodium hydroxide solution was added, What is the percent KHP in the unknown to four significant figures.
The equation is KHP + NaOH ==> H2O + KNaP
moles NaOH = M x L = ??
Convert moles NaOH to moles KHP. That is 1:1 ratio (from the coefficients in the balanced equation) so moles KHP = moles NaOH.
grams KHP = moles KHP x molar mass KHP
%KHP = (grams KHP/0.847)*100 = ??
Note: Your post has only three significant figures in the 0.847 g sample; therefore, you cannot give an answer to four s.f. (unless of course that was 0.8470). A second note, and more troubling, is that you provided no molarity for the NaOH. Without that you can't work the problem anyway.
I don't agree this answer. number %khp so high
To calculate the percent KHP in the unknown, we need to determine the moles of KHP and the moles of NaOH used in the titration.
Step 1: Calculate the moles of NaOH used.
Since we know the volume (19.82 mL) and concentration of NaOH solution is typically given (but it's missing here), we can't determine the exact moles of NaOH used. We need the molarity (concentration) of the NaOH solution to calculate the number of moles.
Step 2: Calculate the moles of KHP used.
The molar mass of potassium hydrogen phthalate (KHP) is 204.22 g/mol.
We have mass = 0.847 g.
Moles of KHP = mass of KHP / molar mass of KHP
Moles of KHP = 0.847 g / 204.22 g/mol
Moles of KHP ≈ 0.004148 mol (rounded to 4 significant figures)
Step 3: Calculate the percent KHP.
To find the percent KHP, we need the ratio of moles of KHP to the total moles present (which includes the moles of NaOH used in the titration).
Total moles = moles of KHP
Percent KHP = (moles of KHP / total moles) x 100
Percent KHP = (0.004148 mol / 0.004148 mol) x 100
Percent KHP = 100%
So, the percent KHP in the unknown sample is 100% to four significant figures.
To find the percent KHP in the unknown sample, we need to determine the amount of KHP present in the sample and then calculate it as a percentage of the total sample weight. Here's how you can do it:
1. Calculate the amount of KHP used in the titration:
- The molar mass of KHP (potassium hydrogen phthalate) is 204.23 g/mol.
- Convert the volume of sodium hydroxide solution added (19.82 mL) to liters by dividing by 1000 (1 mL = 0.001 L).
- Use the concentration of the sodium hydroxide solution to convert the volume to moles of NaOH (Molarity x Volume in L = Moles).
- Since the titration reaction between NaOH and KHP is 1:1, the moles of NaOH used is equal to the moles of KHP.
- Convert the moles of KHP to grams by multiplying by its molar mass.
2. Calculate the percent KHP in the unknown sample:
- Divide the calculated mass of KHP by the initial sample mass (0.847 g) and multiply by 100 to get the percentage.
Let's perform the calculations:
1. Calculating the amount of KHP used in the titration:
- Molar mass of KHP = 204.23 g/mol.
- Volume of NaOH solution used = 19.82 mL = 0.01982 L.
- Concentration of NaOH solution is missing from the question, so I can't provide an exact calculation. However, assuming a typical concentration like 0.1 M, we can proceed with the calculation.
- Moles of NaOH = (0.1 M) x (0.01982 L) = 0.001982 mol.
- Moles of KHP = 0.001982 mol.
Since the ratio between KHP and NaOH is 1:1 (from the balanced equation), the moles of KHP used in the titration are also 0.001982 mol.
- Mass of KHP used = (0.001982 mol) x (204.23 g/mol) = 0.404 g.
2. Calculating the percent KHP in the unknown sample:
- Percent KHP = (mass of KHP used / initial sample mass) x 100.
- Percent KHP = (0.404 g / 0.847 g) x 100 = 47.7% (rounded to four significant figures).
Therefore, the percent KHP in the unknown sample is approximately 47.7%.