Chemistry for Physiology

Ease of separation implies relatively weak bonds. Both ionic and covalent bonds are strong.

Isotonic means that the IV solution has the same concentration of particles (albeit the particles themselves may be different) as in RBC; hence there is no net osmotic flow.

As 0.9% NaCl is isotonic, and 0.45% is less than 0.9%, it must be hypotonic (and there is only one best correct answer!). A is “4% and a fifth” while B is “3.3% and a third”.

The number of moles in 0.9 g = 0.9 g/58.5 g/mol = 0.0154 mol of Na⁺Cl−. However NaCl separates into ions when dissolved, so that there will be 0.0154 mol of Na and 0.0154 mol of Cl; hence 0.0308 osmol of particles = 30.8 mosmol per 100 ml. In 1 L, the number of moles would be ten times greater, so 300 mosmol/L (is closest).

Acidosis = blood pH <7.35. Blood pH less than 7.0 is extremely rare and presages imminent death.

Molecules will flow from areas of high concentration towards areas of low concentration. Hence bicarbonate will flow from the dialysing liquid at 32 to blood at 14 mmol/L, while urea will flow from blood at 23 mmol/L to the dialysing liquid at 0 mmol/L.

Nitrogen is placed in Period VA of the periodic table and so needs to share three electrons. That is, it needs to form three covalent bonds.

As osmolality (osmol/kg) refers to the concentration within a mass (a kilogram) of solution it is unaffected by the temperature of the solution. Osmolarity (with an “r”) in osmol/L refers to the concentration within a volume of a litre of solution. For human physiological solutions which are relatively dilute, there is virtually no difference between the concentrations of solutions when expressed as osmolarity or osmolality.

This is one definition of a molecule.

A buffer has the ability to destroy either acid or base.