What are the medical and pharmaceutical uses of specific chemical compounds and elements, and what are their properties?

Here are the answers to your questions:

• a) Two medical or pharmaceutical uses of $\text{HCO}_3^-$ (bicarbonate):

  • As an antacid to relieve indigestion and heartburn.
  • To treat metabolic acidosis by increasing blood pH.

• b) The ten elements in the second Transition Series (Period 5, d-block) are:

  • Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), Cadmium (Cd).

• c) Two qualities of protective agents:

  • They form a physical barrier on the skin or mucous membranes.
  • They possess mild astringent or adsorbent properties to soothe irritation.

• d) The pharmaceutical significance of $\text{TiO}_2$ (Titanium Dioxide):

  • It is used as a pigment in tablets and capsules, and as an opacifying agent in sunscreens due to its ability to block UV radiation.

• e) Emollient laxatives are substances that soften stool by increasing its water and fat content, making it easier to pass. An example is Docusate sodium.

• f) Two medical uses of Co (Cobalt):

  • As a component of Vitamin $\text{B}_{12}$ (cobalamin), essential for red blood cell formation and neurological function.
  • In radiation therapy for cancer treatment (Cobalt-60).

• g) Two uses of sodium citrate in our bodies:

  • It acts as a buffer to regulate blood pH.
  • It is involved in calcium metabolism and can prevent blood clotting.

• h) The main use of $\text{HPO}_4^{2-}$ (hydrogen phosphate ion) in the human body:

  • It is a crucial component of the phosphate buffer system, which helps maintain the pH balance of blood and intracellular fluids.

• i) Achlorhydria is a condition where the stomach produces little or no hydrochloric acid.

• j) The pharmaceutical importance of silicates:

  • They are used as adsorbents, disintegrants, and glidants in tablet formulations. An example is Magnesium trisilicate, used as an antacid.

• k) One pharmaceutical use of $\text{N}_2$ gas and one medical use of liquid $\text{N}_2$:

  • $\text{N}_2$ gas (nitrogen gas) is used as an inert atmosphere to protect oxygen-sensitive drugs during manufacturing and packaging.
  • Liquid $\text{N}_2$ (liquid nitrogen) is used in cryosurgery for removing warts and other skin lesions.