In an early TV commercial for Rolaids antacid tablets, the manufacturer claimed

Question

In an early TV commercial for Rolaids antacid tablets, the manufacturer claimed that the tablet would neutralize 47 times its own weight of stomach acid. The tablet weighed 1.4 g and contained 0.334 g of the active ingredient, NaAl(OH)_2CO_3 + 4 HCI rightarrow NaCl + AlCl_3 + 3 H_2O + CO_2 How many moles of HCI would one Rolaids tablet neutralize? Stomach acid is about 0.14 M HCI and has a density about the same as water. Did a Rolaids tablet neutralize 47 times its own weight of HCI or 47 times. Its own weight of 0.14 M HCI solution (HCI + water)?

Explanation / Answer

Answer:

Molecular formula of an Active ingradient in antacid is NaAl(OH)2CO3.

Molar mass of NaAl(OH)2CO3. = 144 g/mole.

Mass of NaAl(OH)2CO3.in an antacid = 0.334 g.

# of Moles of NaAl(OH)2CO3 = Given Mass / Molar Mass = 0.334 / 144 = 2.32 x 10-3 moles.

From The given balanced reaction of NaAl(OH)2CO3 with HCl we write mole relationship as,

1 mole of NaAl(OH)2CO3   4 moles of HCl

Then,    2.32 x 10-3 moles of NaAl(OH)2CO3 = 4 x 2.32 x 10-3 moles of HCl

= 9.28 x 10-3.moles of HCl.

0.14 M of HCl means 0.14 moles of HCl in 1000 mL i.e. 1000 g solution (as density equals to 1g/mL).

0.14 moles HCl = 0.14 x 36.5 = 5.11 g.

Mass of Rolaids tablet = 1.4 g.

As per claim, 1 tablet expected to neutralize = 1.4 x 47 = 65.8 g stomach acid.

But 0.14 M HCl means just 5.11 g HCl and hence rest 60.69 g (65.8 - 5.11 = 60.69 ) must be water.

So Company claims that, 1 Rolaids tablet neutralizes 47 times its own wight of 0.14 M HCl i.e. (HCl + Water).

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