16. A doctor prescribed antacid tablets
made from magnesium hydroxide
to a student who was suffering
from excess stomach acid:
(a) Why did the doctor prescribe
the antacid tablets?
(b) Write a balanced chemical
equation that took place in the
student’s stomach after taking
the tablets.
(c) If the normal acid content
in the stomach is 160.00
millimolar and the stomach
secrets 0.50 litres of gastric
juice in a day, calculate the
mass of the tablets to be given
to the student if the gastric
juice had 210.00 millimolar
hydrochloric acid.
(d) If each tablet of an antacid
weighs 145 mg of magnesium
hydroxide, how many tablets
will the student be given?
(e) If a dose requires 1 tablet per
every 12 hours, how many
days should the student take
to finish the full dose?
(a) The doctor prescribed the antacid tablets to the student because they were suffering from excess stomach acid. Antacids containing magnesium hydroxide can help neutralize the excess acid and provide relief from symptoms such as heartburn and indigestion.
(b) The balanced chemical equation for the reaction that takes place in the student's stomach after taking the antacid tablets is:
2Mg(OH)2 + 2HCl -> 2MgCl2 + 2H2O
(c) To calculate the mass of the tablets needed, we can use the formula:
Mass (in grams) = molarity (in mol/L) * volume (in L) * molecular weight (in g/mol)
First, let's convert the gastric juice volume from liters to milliliters: 0.50 L = 500 mL.
Next, let's calculate the number of moles of hydrochloric acid present in the gastric juice:
Moles of HCl = molarity * volume (in L)
Moles of HCl = 210.00 mM * 0.50 L
Moles of HCl = 0.210 mol
Now, let's calculate the mass of the tablets needed:
Mass (in g) = 0.210 mol * 58.33 g/mol (molar mass of Mg(OH)2)
Mass (in g) = 12.2 g
Therefore, the mass of the tablets to be given to the student is 12.2 grams.
(d) The weight of each tablet is given as 145 mg. To convert this to grams:
Weight of each tablet = 145 mg / 1000 = 0.145 g
Now, we can calculate the number of tablets the student will be given:
Number of tablets = Mass needed / Weight of each tablet
Number of tablets = 12.2 g / 0.145 g
Number of tablets ≈ 84 tablets (rounded to the nearest whole number)
Therefore, the student will be given approximately 84 tablets.
(e) If a dose requires 1 tablet every 12 hours, we need to determine how many tablets the student needs for the full dose.
Number of tablets per day = 1 tablet every 12 hours * 2 doses per day = 2 tablets per day
To calculate the number of days the student should take to finish the full dose:
Number of days = Number of tablets / Number of tablets per day
Number of days = 84 tablets / 2 tablets per day
Number of days = 42 days
Therefore, the student should take the full dose for 42 days.