Question

part b - multiple choice

1. which subatomic particle determines the identity of an element?

a) proton
b) neutron
c) electron
d) nucleus

1. which element would you expect to be the most stable?

a) sodium (na)
b) chlorine (cl)
c) neon (ne)
d) magnesium (mg)

1. which of the following best describes a base?

a) tastes sour, ph < 7
b) produces h+ ions in solution
c) produces oh- ions in solution
d) neutral ph

1. which equation is already balanced?

a) h2 + o2 → h2o
b) n2 + 3h2 → 2nh3
c) na + cl2 → nacl
d) c + o2 → co

1. which reaction is endothermic?

a) burning paper
b) melting ice
c) fireworks
d) combustion of gasoline

Explanation:

1. The number of protons in an atom determines its atomic number and thus the identity of the element.
2. Neon is a noble - gas with a full outer electron shell, making it very stable.
3. Bases produce OH⁻ ions in solution. Acids produce H⁺ ions, taste sour and have pH < 7, and neutral pH is 7.
4. For the reaction N₂ + 3H₂ → 2NH₃, there are 2 nitrogen atoms and 6 hydrogen atoms on both sides of the equation. In other options, the number of atoms on both sides is not equal.
5. Melting ice requires heat input (endothermic). Burning paper, fireworks, and gasoline combustion release heat (exothermic).

Answer:

1. a) Proton
2. c) Neon (Ne)
3. c) Produces OH⁻ ions in solution
4. b) N₂ + 3H₂ → 2NH₃
5. b) Melting ice