QUESTION $1$

$1\mathrm{.}1$ Calcium oxalate monohydrate $($CaC$2$O$4.$H$2$O$)$ is a material quite often used as a

standard reference material in thermogravimetric analysis due to its well$-$known

process of thermal decomposition. Its decomposition in an inert atmosphere can be

divided into three sequential steps, namely dehydration at $160$C followed by

decomposition to calcium carbonate at $380$C and final thermal decomposition to

calcium oxide $($CaO$)$ at $750$C$.$

$($a$)$ Sketch out the typical weight loss curve as a function of temperature $($Clearly

marking all sequential steps$).(10)$

$($b$)$ Write down the sequential balanced decomposition reactions that calcium

oxalate monohydrate undergoes on each step. $(5)$

$($c$)$ Calculate the expected sample weight $($as a percentage of the initial mass of

CaC$2$O$4.$H$2$O$)$ after each step. $(10)$

$($d$)$ A sample of mixed calcium oxalate monohydrate and anhydrous silica weighs

$7\mathrm{.}020$ mg$.$ After heating to $750\backslash$deg C$,$ the weight of the mixture was $6\mathrm{.}560$ mg$.$ What

was the weight of calcium oxalate in the original sample? $(5)$

$1\mathrm{.}2$ Briefly describe how Differential Scanning Calorimetry $($DSC$)$ work? $(6)$

$[36]$

QUESTION $2$

$2\mathrm{.}1$ Your ability to interpret TG and DTG curves is of paramount importance in order

to demonstrate your competency in advanced analytical techniques course. With

reference to Figure $1$ below, briefly explain what TG and DTG curves $($i$)($vii$)$

represent? $(14)$

$3$

Figure $1$: TG and DTG curves

$2\mathrm{.}2$ Figure $2$ depicts a typical Differential Scanning Calorimetry Thermogram curve.

Carefully look at the curve and mention processes represented by A $$ E$.$

$(5)$

Figure $2$: Differential Scanning Calorimetry Thermogram curve

B

C

D

E

A

$4$

$2\mathrm{.}3$ What are the major differences between thermogravimetric analysis $($TGA$)$ and

Derivative Thermogravimetry $($DTG$)$ with regards to the thermal curve output? $(2)$

$2\mathrm{.}4$ What are the similarities and differences between Differential Thermal Analysis

$($DTA$)$ and Differential Scanning Calorimetry $($DSC$).(3)$