A student performs an experiment involving Alka$-$Seltzer and water in an Erlenmeyer flask and uses a stopper to close the system $($see below$).$ She collects the following data.

Table $1.$ Alka$-$Seltzer in a Closed System Experiment

$\backslash$table$[[,$BEFORE:,AFTER:$],[\backslash$table$[[$Experimental$],[$Set$-$Up$]],\backslash$table$[[$Erlenmeyer flask$],[$containing $100],[\frac{1}{2}$ alka seltzer tablet$],[($outside of Erlenmeyer$],[$flask$)]],\backslash$table$[[$Erlenmeyer$],[$flask containing$],[100mL$ water$],[$and $\frac{1}{2}$ alka$],[$seltzer tablet,$],[$with stopper on$],[$top of flask.$]]],[$Mass Trial $1$:$,243\mathrm{.}39g,243\mathrm{.}38g$