A 0.2027 gram sample of finely powdered limestone (mainly CaCO₃) was dissolved in 50 mL of 0.1035 M HCl. The solution was heated to expel CO₂ produced by the reaction. The remaining HCl was then titrated with 0.1018M of NaOH and it required 16.62 mL. Calculate the percentage of CaCO₃ in the limestone sample? CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

Explanation:

CaCO₃     +     2HCl     →      CaCl₂    +    CO₂       +       H₂O

100 gm  +  2000 mL of M HCl

Amount of HCl remaining = .1018 M of 16.62 mL

= .1018 x 16.62 mL of M HCl

= 1.69 mL of M HCl

Initial HCl taken = 50 mL of .1035 M HCl

= 5.175 mL of M HCl

HCl reacted = 5.175 - 1.69 mL of M HCl

= 3.485 mL of  M HCl

2000 mL of M HCl reacts with 100 gm of CaCO₃

3.485 mL of M HCl will react with .174 grams of CaCO₃

percentage of calcium carbonate = .174 x 100 / .2027

= 85.84 %

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.