Typical room temperature is 23°c. in a classroom at sea level, the atmospheric pressure is 1.00 atm, would the gas in a balloon held in this classroom be at stp?

No the given gas is not at STP.

Explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number of particles.

Standard condition of temperature (STP)  is 273 K and atmospheric pressure is 1 atmosphere respectively.  

Given temperature :

1 mole of every gas occupy volume at STP = 22.4 L

Thus at STP, the temperature is 273 K and pressure is 1 atmosphere and the given gas is not at STP.

< > according to newton's third law of motion, forces always act in equal but opposite pairs. another way of saying this is for every action, there is an equal but opposite reaction.< >