If z is the symbol for an element, which pair among the following represents isotopes of the same element?
a. 51 51
z and z
25 26
b. 51 50
z and z
25 25
c. 50 50
z and z
25 27
d. 51 50
z and z
26 25

Agas at 155 kpa and standard temperature has an initial volume of 1.00 l. the pressure of the gas rises to 500 kpa as the temperature also rises to 135°c. what is the new volume? 2.16 l 0.463 l 0.207 l 4.82 l

List four observations that indicate that a chemical reaction may be taking place

Compare and contrast physical changes with chemical changes.