HELP EASY!! Which of the following most likely happens during a chemical change?
A) No new substances are formed
B) Properties of a substance remain unchanged
C) Composition of a substance is same as before.
D) Different substances than before are produced

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

Lab reagent, hypothesis test.a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl.these six measurements are assumed to be an srs of all possible measurements from solution.they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution.carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.

In which reaction is precipitation occurring?