Para que la ecuación CH4 + XO2 — YCO2 + ZH20 cumpla con la
ley de conservación de masa,
los valores de X, Y y Z deben ser
respectivamente:
A) 1,2,3
B) 3, 2, 1
C) 2,1,2
OD) 2, 2, 1
O E) 1, 2, 2

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

What effect would average population growth have on land usage? a. urban use of land would rise to more than 30 percent of available land. b. industrial use of land would rise to more than 30 percent of available land. c. the percentage of available land used as cropland would stay the same. d. cropland would fall to about 10 percent of available land.

11) burning your hand when accidentally touching a hot plate is an example of which heat transfer? a. conduction b. convection c. radiation d. none of these