A patient is suspected of having low stomach acid, a condition known as hypochloridia. To determine whether the patient has this condition, her doctors take a 15.00 mL
sample of her gastric juices and titrate the sample with 3.99×10−4 M KOH.
The gastric juice sample required 9.23 mL
of the KOH
titrant to neutralize it.
Calculate the pH of the gastric juice sample. Assume the sample contained no ingested food or drink which might otherwise interfere with the titration.
At first I came up with 4.61 but that isn't correct. I recalculated and got 10.61 but that was also incorrect. Help?
To calculate the pH of the gastric juice sample, you need to determine the concentration of H+ ions in the sample using the volume and concentration of the titrant used. Here's how you can do it:
1. Convert the volume of the KOH titrant used to liters: 9.23 mL = 0.00923 L
2. Use the balanced equation between KOH and HCl to determine the moles of KOH used:
1 mole of KOH reacts with 1 mole of HCl
Therefore, moles of KOH = moles of HCl = concentration of KOH × volume of KOH titrant
moles of KOH = (3.99×10^(-4) M) × (0.00923 L)
3. Determine the moles of H+ ions in the gastric juice sample, considering the 1:1 stoichiometry between HCl and H+ ions.
4. Calculate the concentration of H+ ions in the gastric juice sample by dividing the moles of H+ ions by the original volume of the sample: concentration of H+ ions = moles of H+ ions / volume of gastric juice sample
Note: The volume of the gastric juice sample is given as 15.00 mL = 0.015 L
5. Calculate the pH of the gastric juice sample using the formula: pH = -log[H+ ions]
Now, you can work out the calculations to find the pH of the gastric juice sample.
To calculate the pH of the gastric juice sample, we need to determine the concentration of hydrogen ions present in the sample.
First, let's find the number of moles of KOH used in the titration:
Moles of KOH = concentration of KOH * volume of KOH used
= (3.99×10^-4 mol/L) * (9.23 mL * 1 L/1000 mL)
= 3.68×10^-6 mol
Since KOH reacts with HCl in a 1:1 ratio, the number of moles of HCl in the gastric juice sample is also 3.68×10^-6 mol.
Now, let's calculate the concentration of HCl in the gastric juice sample:
Concentration of HCl = moles of HCl / volume of gastric juice sample
= 3.68×10^-6 mol / 15.00 mL
= 2.45×10^-4 mol/L
Since the concentration of HCl is equal to the concentration of hydrogen ions (H+), the pH of the gastric juice sample can be calculated using the formula:
pH = -log[H+]
pH = -log(2.45×10^-4)
= -(-3.61)
= 3.61
Therefore, the pH of the gastric juice sample is 3.61.