Calculate: The % w/v of NaCl present in the infusion. The % of stated content of NaCl.

Question

An infusion stated to contain 0.95% w/v NaCl was diluted so that its Na content could be determined by flame photometry. The following dilutions were carried out:

(i) 10 ml of the sample was diluted to 250 ml with water.

(ii) 10 ml of the diluted sample was diluted to 200 ml with water.

The sample was found to contain 0.74 mg/100 ml of Na.

Atomic weights: Na = 23 Cl = 35.5

Calculate:

The % w/v of NaCl present in the infusion.

The % of stated content of NaCl.

Answer 1

Which sample was found to contain 0.74 mg/100 ml, and it should probably read 0.74 mg Na/100 ml rather than 0.74 mg/100 ml Na.

Was this the amount of Na in (i) or in (ii)?