Which of the following statements describes all the variables in an experiment?
A.
All variables are measured to provide data for the experimental results.
.
B.
All variables are kept the same from one part of the experiment to another.
OC.
All variables affect the results of the experiment.
O
D.
All variables are changed from one part of the experiment to another.

What are the spectator ions in 2h+ + so42- + ca2+ + 2r → caso4 + 2h+ + 21?

Two nitro no2 groups are chemically bonded to a patch of surface. they can't move to another location on the surface, but they can rotate (see sketch at right). it turns out that the amount of rotational kinetic energy each no2 group can have is required to be a multiple of ε, where =ε×1.010−24 j. in other words, each no2 group could have ε of rotational kinetic energy, or 2ε, or 3ε, and so forth — but it cannot have just any old amount of rotational kinetic energy. suppose the total rotational kinetic energy in this system is initially known to be 32ε. then, some heat is removed from the system, and the total rotational kinetic energy falls to 18ε. calculate the change in entropy. round your answer to 3 significant digits, and be sure it has the correct unit symbol.

Achemist has dissolved a certain substance in water. the chemist knows that more of the substance could be dissolved into the water before it stops dissolving. therefore