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%.