From the given list, the number of compounds with +4 oxidation state of Sulphur ________.

$$\mathrm{SO}_3, \mathrm{H}_2 \mathrm{SO}_3, \mathrm{SOCl}_2, \mathrm{SF}_4, \mathrm{BaSO}_4, \mathrm{H}_2 \mathrm{S}_2 \mathrm{O}_7 $$

<p><style type="text/css"> .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px; overflow:hidden;padding:10px 5px;word-break:normal;} .tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px; font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;} .tg .tg-baqh{text-align:center;vertical-align:top} </style> <table class="tg" style="undefined;table-layout: fixed; width: 724px"> <colgroup> <col style="width: 157px"> <col style="width: 72px"> <col style="width: 108px"> <col style="width: 94px"> <col style="width: 79px"> <col style="width: 105px"> <col style="width: 109px"> </colgroup> <thead> <tr> <th class="tg-baqh">Compounds</th> <th class="tg-baqh">$\mathrm{SO_3}$</th> <th class="tg-baqh">$\mathrm{H_2SO_3}$</th> <th class="tg-baqh">$\mathrm{SOCl_2}$</th> <th class="tg-baqh">$\mathrm{SF_4}$</th> <th class="tg-baqh">$\mathrm{BaSO_4}$</th> <th class="tg-baqh">$\mathrm{H_2S_2O_7}$</th> </tr> </thead> <tbody> <tr> <td class="tg-baqh">O.S. of Sulphur:</td> <td class="tg-baqh">+6</td> <td class="tg-baqh">+4</td> <td class="tg-baqh">+4</td> <td class="tg-baqh">+4</td> <td class="tg-baqh">+6</td> <td class="tg-baqh">+6</td> </tr> </tbody> </table></p> <br/><p>To determine the number of compounds with a +4 oxidation state of sulfur, we need to examine the oxidation states of sulfur in each of the listed compounds. The +4 oxidation state means that sulfur has lost 4 electrons compared to its elemental state.</p> <p>Let's go through each compound:</p> <ul> <li>$\mathrm{SO}_3$: Sulfur trioxide. In this compound, sulfur exhibits a +6 oxidation state because each oxygen contributes -2, for a total of -6 (3 oxygens), which must be balanced by sulfur to maintain a neutral charge. So, this compound does not have sulfur in the +4 oxidation state. </li> <br/><li>$\mathrm{H}_2 \mathrm{SO}_3$: Sulfurous acid. Here again, with two hydrogens (each contributing +1 = total +2) and three oxygens (each contributing -2 = total -6), sulfur has an oxidation state of +4 to balance out the -4 from the oxygens and +2 from the hydrogens. This compound does have sulfur in the +4 oxidation state.</li> <br/><li>$\mathrm{SOCl}_2$: Thionyl chloride. Sulfur in this compound is connected to two chlorine atoms and one oxygen atom. Chlorine generally has an oxidation state of -1 (total -2 for both Cl atoms) and oxygen -2. To balance the -4 charge (from one oxygen and two chlorines), sulfur must have an oxidation state of +4. This compound has sulfur in the +4 oxidation state.</li> <br/><li>$\mathrm{SF}_4$: Sulfur tetrafluoride. Fluorine is almost always in the -1 oxidation state, and there are four fluorine atoms for a total of -4. To balance this, sulfur must have a +4 oxidation state, making this compound one with sulfur in the +4 oxidation state.</li> <br/><li>$\mathrm{BaSO}_4$: Barium sulfate. Barium has a +2 oxidation state, and sulfate (SO4) as a whole must have a -2 oxidation state to balance the barium. In sulfate, sulfur has an oxidation state of +6 (since each oxygen is -2 for a total of -8, and +6 from sulfur balances it to -2 overall). Hence, sulfur does not have a +4 oxidation state in this compound.</li> <br/><li>$\mathrm{H}_2 \mathrm{S}_2 \mathrm{O}_7$: Pyrosulfuric acid or oleum. Each hydrogen is +1 (total +2), and the seven oxygens are -2 each (total -14). To balance -12 (total of oxygens and hydrogens), each sulfur must have an oxidation state of +6. Therefore, sulfur is not in the +4 oxidation state in this molecule.</li> </ul> <p>So, from the given list, only three compounds have sulfur in the +4 oxidation state: $\mathrm{H}_2 \mathrm{SO}_3$, $\mathrm{SOCl}_2$, and $\mathrm{SF}_4$. Therefore, the number of compounds with a +4 oxidation state of sulfur is three.</p>