Directions: On the line before each question or statement, write the letter of the correct answer. 1. Some substances are chemically combined in specific combinations. These are
A. compounds.
B. homogeneous mixtures.
C. heterogeneous mixtures.
2. Which item is a form of matter?
A. air
B. sound
C. gravity
3. Which item is a substance?
A. trail mix
B. table salt
C. breakfast cereal

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.  

hypostyle hall;