a) Electrons
b) Neutrons
c) Protons
d) Helium nuclei
Alpha decay occurs when an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons (a helium nucleus). This type of radiation is relatively large and can be stopped by a sheet of paper or skin.
a) It is consumed during the reaction.
b) It increases the activation energy.
c) It speeds up the reaction without being consumed.
d) It slows down the reaction.
A catalyst increases the rate of a chemical reaction by lowering the activation energy required. Importantly, a catalyst is not consumed during the reaction and can be used repeatedly.
a) 1s² 2s² 2p⁶ 3s²
b) 1s² 2s² 2p⁶ 3s¹
c) 1s² 2s² 2p⁶ 3p¹
d) 1s² 2s² 2p⁶ 3s² 3p⁶
Sodium (Na) has an atomic number of 11, so it has 11 electrons. The correct electron configuration is 1s² 2s² 2p⁶ 3s¹, with the last electron in the 3s orbital. This shows that sodium has one electron in its outermost shell, making it highly reactive.
a) NaCl
b) CO₂
c) CH₄
d) H₂O
Organic compounds typically contain carbon-hydrogen bonds. Methane (CH₄) is an organic compound because it consists of carbon bonded to hydrogen. NaCl (sodium chloride), CO₂ (carbon dioxide), and H₂O (water) are inorganic compounds.
a) Na
b) Cl
c) O
d) N
Alkali metals are found in Group 1 of the periodic table. Sodium (Na) is an alkali metal, known for being highly reactive, especially with water. Chlorine (Cl), oxygen (O), and nitrogen (N) are nonmetals, not alkali metals.
a) 18.02 g/mol
b) 28.02 g/mol
c) 36.04 g/mol
d) 44.01 g/mol
The molar mass of water is calculated by adding the atomic masses of hydrogen (H) and oxygen (O). Hydrogen has an atomic mass of approximately 1.008 g/mol, and oxygen has an atomic mass of approximately 16.00 g/mol. Therefore, the molar mass of H₂O is (2 × 1.008) + 16.00 = 18.02 g/mol.
a) H₂CO₃
b) HCl
c) H₂SO₄
d) CH₃COOH
Hydrochloric acid (HCl) is a strong acid because it completely dissociates into H⁺ and Cl⁻ ions in water. H₂SO₄ (sulfuric acid) is also a strong acid, but H₂CO₃ (carbonic acid) and CH₃COOH (acetic acid) are weak acids because they do not dissociate completely in water.
a) 0
b) 7
c) 14
d) 1
The pH scale ranges from 0 to 14, with 7 being considered neutral. A neutral solution is one where the concentration of hydrogen ions (H⁺) equals the concentration of hydroxide ions (OH⁻), which occurs in pure water at 25°C. A pH below 7 is acidic, and a pH above 7 is basic.
a) H₂O
b) NaCl
c) CO₂
d) O₂
Ionic bonds are formed when electrons are transferred from one atom to another. In NaCl, sodium (Na) donates an electron to chlorine (Cl), resulting in a positively charged sodium ion (Na⁺) and a negatively charged chloride ion (Cl⁻), forming an ionic bond. In contrast, H₂O, CO₂, and O₂ all involve covalent bonds where electrons are shared between atoms.