[Shabbar]

I know that Sulphur does not react with dilute acids but it does react with concentrated acids. For e.g.

S + 6HNO₃ --> H₂SO₄ + 2H₂O + 6NO₂
S + 2H₂SO₄ --> 3SO₂ + 2H₂O

Now, my question is how to easily remember these reactions involving concentrated acids? Is there like a pattern or clue?

[Borek]

There is kind of logic here. Sulfur can be oxidized either to S(IV) (SO₂ and/or sulfurous acid)  or S(VI) (SO₃ and/or sulfuric acid). When reacting with the nitric acid (and probably perchloric acid) it can be oxidized all the way to S(VI). When reacting with the sulfuric acid even if it were oxidized to S(VI) sulfur from the sulfuric acid would be reduced at the same time, so the overall reaction can't produce anything above S(IV).