Chemistry for Physiology

0.18% means 0.18 g per 100 ml of solution.

Healthy blood is slightly alkaline. Acidosis is applied to blood with pH below the normal range of 7.35–7.45. If blood has pH <7.35, it is not sufficiently alkaline.

A pH change of one corresponds to a change in hydronium ion concentration by a factor of 10. As the pH has risen, the acidity has decreased, so there are fewer hydronium ions. That is 1/10 of 0.19% = 0.019%

(By calculation) Percent concentration refers to how many grams are dissolved in 100 ml of solution.One mole of glucose has a mass of 180 g. (6 × 12) + (12 × 1) + (6 × 16) = 180.12 mmol/L = 0.012 mol/Lmol/L = (mass/L)÷(mass of 1 mol): hence 0.012 mol/L = (mass/L)÷180; so mass = 180 × 0.012 = 2.16 g/ L2.16 g/L = 0.216 g/100 ml = 0.216%(Alternatively: The answer can’t be 5% as this is an isotonic glucose solution. Hence neither is it 12% as this is hypertonic. % conc is not the same number as mol/L, so the answer is not A.)

Osmosis is the diffusion of WATER molecules through a membrane, from where there is a higher concentration of water molecules to where there is a lower concentration of water molecules (i.e. into the more concentrated solution).

The number of moles of a substance in a solution is determined by dividing the mass of dissolved substance by the mass of 1 mol of the substance. One mole of chloride has a mass of 35.5 g: 105 mmol/L = 0.105 mol/L. So 0.105 mol/L = mass of Cl (in gram) ÷ 35.5. Rearrange this formula, hence mass of Cl = 35.5 × 0.105 = 3.73 g/L

Isotonic means the same number of solute particles per litre. Choice B would also be correct if “moles” was replaced with “moles per litre”.

Blood is buffered, so very little pH change will result from the addition of acid. Certainly it is not enough to change the pH by 0.1.

Aspirin in an acidic environment will be in its molecular form (and un-ionised). This makes it soluble in non-polar media like the plasma membrane (which is lipid). Being soluble in lipid, molecular aspirin is able to be absorbed from the stomach.

Osmosis refers to movement of water molecules (not other molecules), by diffusion.