PROBLEMS

$11\mathrm{.}1$ Under what circumstances may composite samples be preferred over grab samples, and for what reasons?

$11\mathrm{.}2$ Briefly describe the differences between volumetric, colorimetric, and gravimetric analyses.

$11\mathrm{.}3$ What are the requirements to make precipitation methods reliable?

$11\mathrm{.}4$ What precautions must be taken in the use of crucibles or dishes in gravimetric work?

$11\mathrm{.}5$ To what temperature should dishes be pretreated in order to condition them prior to gravimetric analysis?

$11\mathrm{.}6$ Explain the significance of the drying and ignition temperatures of $103$ and $600C,$ respectively, in analysis of environmental samples.

$11\mathrm{.}7$ Explain why it is necessary $($a$)$ to cool a sample to room temperature before weighing, and $(b)$ to allow the sample to cool in a desiccator.

$11\mathrm{.}8$ What facilities are needed for volumetric analysis?

$11\mathrm{.}9$ What two different types of calibrated glassware are available for volumetric analysis?

$11\mathrm{.}10$ What precautions must be taken with the use of a volumetric pipet?

$11\mathrm{.}11$ What is a standard solution? What is an equivalent solution?

$11\mathrm{.}12$ What is the difference between a primary standard and a secondary standard?

$11\mathrm{.}13$ Determine the equivalent weights of the following materials in grams: $(a)H_{2}S{O}_4$;$(b)HCl$;$(c)Ca(OH{)}_2$;$(d)C{H}_3\frac{C}{O}OH.$

Answer: $($a$)49$; $($b$)36\mathrm{.}5$ ; $($c$)37$;$(d)60$

$11\mathrm{.}14$ Determine the equivalent weights of the following materials in grams:

$($a$)KMn{O}_4$ as an oxidizing agent in acid solutions

$($b$)A{g}_{2}S{O}_4$ in a precipitation reaction involving silver

$($c$)K_{2}C{r}_2{O}_7$ as an oxidizing agent

$($d$)BaC{l}_2$ in a precipitation reaction involving barium