Acompound that changes color when it comes into contact with an acid or base is an?

Suppose the universe were completely empty except for one object-a solid sphere moving through space of 100 km/s. what sort of path would the object be moving in? explain your answer

Can someone me with 3 and 4 plz. this is for masteries test.

‘which reaction would most likely require the use of an inert electrode?