During an experiment, a student observes the formation of a precipitate. why does this indicate that a chemical reaction is likely occurring?

1)a solid forms, and there is a change of color.
2)a gas forms, and there is a change of color.
3)a solid forms, and light is emitted.
4)a gas forms, and light is emitted.

Concerning the 10.0 ml of 0.50 m nacl to 100 ml of solution: when a solution is diluted, does it change the number of moles dissolved?

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line

12. calculate the hydroxide ion concentration of a solution with ph = 3.25. show all calculations leading to an answer