A chemical change occurs when two or more substances react to form one or more new substances. Which of the following best completes this statement about a chemical reaction? In a chemical reaction, . . .

A. Atoms are neither created nor destroyed.

B. Some atoms from the reactants may be lost.

C. Extra atoms are always gained in the product.

D. Extra atoms are added to the product, if needed.

Agas has a volume of 0.7 l at 300 mmhg. what would be the new volume at 900 mmhg

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.

What is the independent variable in this investigation? mass volume sample number substance density