(a) A bulk sample contains grains of two types, both having an approximate spher

Question

(a) A bulk sample contains grains of two types, both having an approximate spherical radius of 0.40 mm. The

two types of grain can be distinguished, under microscopic examination, by their appearance.
Approximately 30 % of the grains are of type-A, which are known to contain approximately 40 % by weight of the analyte. Type-A grains have a density of 2.10 g/cm3.

Type-B grains are known to contain no analyte at all, and Type-B grains have a density of 1.00 g/cm3.
(i) What must the minimum number of grains (particles) be in the gross sample in order to keep the relative sampling uncertainty below 0.5 %? (5 marks)
(ii) Hence, calculate the mass that should be sampled. (2 marks)
(iii) What will be the action plan if the mass to be sampled is NOT sufficiently available at the field? (2 marks)

Explanation / Answer

1) The minimum number of grain particles required at 0.5% is

= 30% * 2.10 + 70% 1.00

=1.33 g/cm3

2) To calculate mass that should be sample

= 30% * 40% + 70% * 0%

= 12%

3) The action plan is to increase the sample size, since there is NO sufficiently in field, we can use the dummpy sample values based on the distribution of the avialbe data points.

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