Which profile best describes the reaction C(s) + 2H2(g) → CH4(9),
AH = -74.9 kJ?

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 is the empirical formula of c6h18o3? ch3o c2h5o c2h6o c2h5o5

Which statement correctly identifies the scientific question and describes why the question is scientific? question 1 refers to the supernatural. question 2 reflects a moral or social value. question 3 refers to something that can be measured. question 4 reflects a question that can’t be observed.