Various odds during heads-up.

odds of hitting a pair in 5 cards is about 50%.

Are these estimates in the right ballpark (excluding stuff like straight, flush, etc)

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Pocket 10s (75%)
vs.
J 9 (25%)

Is this about right, since only a possible J pairing can beat the 10s?

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Pocket 10s (50%)
vs.
J Q (50%)

Is this about right, since either possible J pairing can beat the 10s?

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Pocket 10s (90%)
vs.
8 9 (10%)

Is this about right, since neither possible 8 or 9 pairing can beat the 10s?
(But trips will beat the 10)

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Anyone know the exact odds for the situations above?
What App can I use to do this myself?

Tens versus J9 is 70-30. Versus QJ it's 55-45 (most pairs have a bit of an edge against two over cards). Against 98 the tens are about 85-15. PokerStove would tell you all this, as well as a multitude of online web based odds calculators. In fact CC has its very own odds calculator for this purpose, and there's a sticky for it at the top of this board here you posted your question in.