1.3188g of antacid is weighed and mixed with 75.00 mL of excess 0.1746 M HCl. The excess wcid required 27.20 mL of 0.09767 M NaOH for back titration. Calculate the amount of CaCO3 in the tablet.

The amount of CaCO₃ in the tablet : 0.5219 g

Reaction

1. CaCO₃(in antacid) + 2HCl⇒ CaCl₂+H₂CO₃

2. Titration ⇒ HCl+NaOH⇒NaCl+H₂O

For titration :

M₁V₁.n₁=M₂V₂n₂(n=acid/base valence⇒NaOH/HCl=1)

mol HCl=mol NaOH = excess HCl

mol HCl

Moles of HCl used (reacted with CaCO₃) :

initial HCl - excess HCl =

From reaction 1 :

mol HCl : mol CaCO₃ = 2 : 1

mass of CaCO₃ :

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

b. examine and describe cells