(Solved): I just need help with question 6, please! Experimental Procedure Prepare a solution of sodium metabo ...

Experimental Procedure Prepare a solution of sodium metaborate, ${\mathrm{NaBO}}_2$, by dissolving $4.75\mathrm{g}(0.0125\mathrm{mole})$ of borax, ${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7.10{\mathrm{H}}_2\mathrm{O}$ and $1\mathrm{g}(0.025$ mole $)$ of sodium hydroxide in $20\mathrm{mL}$ of warm water. Cool this mixture in ice and then slowly add $5.75\mathrm{mL}$ of 30 per cent hydrogen peroxide diluted with $15\mathrm{mL}$ of water. Keep the flask in ice and stir for about $15\min$ utes, or until the crystallization of sodium peroxoborate appears to be complete. If the crystals do not appear after 15 minutes, try seeding the solution with a seed crystal obtained from one of the other students in the class. Alternatively, add $30\%$ hydrogen peroxide dropwise until precipitation initiates. Do not add more than 20 drops. This will help initate the precipitation by a "salting out" effect. Filter the crystals under suction, wash with alcohol and ether, and dry. On the basis of chemical analysis, one might write the formula as ${\mathrm{NaBO}}_2?{\mathrm{H}}_2{\mathrm{O}}_2?3{\mathrm{H}}_2\mathrm{O}$ or ${\mathrm{NaBO}}_3?4{\mathrm{H}}_2\mathrm{O}$, but the crystal structure indicates that the formula is more accurately written as ${\mathrm{Na}}_2{\mathrm{B}}_2{\left({\mathrm{O}}_2\right)}_2(\mathrm{OH}{)}_4?6{\mathrm{H}}_2\mathrm{O}$. Qualitatively test approximately $0.1\mathrm{g}$ samples of the sodium peroxoborate you have prepared. If a balance is not conveniently available, $0.1\mathrm{g}$ can be estimated to be about the volume of solid sample approximating the volume of a small pea. To the $0.1\mathrm{g}$ sample of the sodium peroxoborate, add $6\mathrm{mL}$ of $0.1\mathrm{N}\mathrm{HCl}$. To this acidified solution, add 0.1 molar ${\mathrm{KMnO}}_4$ solution dropwise. Observe the results. Write equations for the reactions. Was ${\mathrm{Mn}}^2+$ or ${\mathrm{Mn}}^4+$ formed? To another $0.1\mathrm{g}$ sample of the sodium peroxoborate, add $6\mathrm{mL}$ of $0.1\mathrm{N}\mathrm{HCl}$. To this acidified solution, add dropwise a fresh solution of $1.65\mathrm{g}\mathrm{KI}$ in $100\mathrm{ml}$, water $(0.165\mathrm{g}$ SODIUM PEROXOBORATE 159 $\mathrm{KI}$ in $10\mathrm{mL}$ water if the $\mathrm{KI}$ is made up individually by each student). Observe the results. Write equations for the reactions. Questions to be Considered 1. If the solution of sodium metaborate prepared in this experiment is evaporated, borax will crystallize out. Explain. 2. A solution of borax in water is quite strongly alkaline. Explain. Why can borax be regarded as an acid salt? 3. How would you attempt to prepare solid ${\mathrm{NaBO}}_2$ ? 4. Compare the structural formula for sodium peroxoborate with the formula of perchloric acid. 5. Assume that you have a 0.1 molar solution of sodium peroxoborate. What percent would be decomposed to hydrogen peroxide? 6. Write a balanced equation describing what happens in the permanganate test and the iodide test.