General information:
Atropine (B) is a weakly basic compound. It partially ionizes in water to produce protinated atropine (BH+) and hydroxyl ions (OH-) according to the following formula:
Assuming that it has Kb value of 4.5 × 10-5 and a molar mass (molecular weight) equal to 289.4 g/ mole then pH of the solution can be calculated as the following.
Calculations:
Step 1. Calculation of molar concentration.
Molar concentration = (0.1g/ 100ml) × (1000 ml/ liter) × ( 1/ (289.4 g/ mole) = 0.0035 mole/ liter.
Step 2. Calculation of pH by applying the following equations:
[OH-] = (-(4.5 × 10-5) + sqrt((4.5 × 10-5)2+(4 × 4.5 × 10-5 × 0.0035)))/ 2
[OH-] = 3.75 × 10-4
pH = 14 + log (3.75 × 10-4) = 10.57
Check that the pH of 0.0035 M atropine (Kb = 4.5 × 10-5) solution is equal to 10.57 using online pH calculator.
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Atropine (B) is a weakly basic compound. It partially ionizes in water to produce protinated atropine (BH+) and hydroxyl ions (OH-) according to the following formula:
B
+ H2O ↔ BH+ + OH-
Calculations:
Step 1. Calculation of molar concentration.
Molar concentration = (0.1g/ 100ml) × (1000 ml/ liter) × ( 1/ (289.4 g/ mole) = 0.0035 mole/ liter.
Step 2. Calculation of pH by applying the following equations:
[OH-] = (-(4.5 × 10-5) + sqrt((4.5 × 10-5)2+(4 × 4.5 × 10-5 × 0.0035)))/ 2
[OH-] = 3.75 × 10-4
pH = 14 + log (3.75 × 10-4) = 10.57
Check that the pH of 0.0035 M atropine (Kb = 4.5 × 10-5) solution is equal to 10.57 using online pH calculator.
Related posts:
Calculating pH of a weak base solution.
What is an acid? what is a base?
Calculate pH of 0.1% w/v methylparaben solution.
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