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HESI: Chemistry Questions and
Answers | Latest Version | 2025/2026 | Correct & Verified
The atomic number of an element represents the number of protons in its nucleus.✔✔The number of electrons in a neutral atom is equal to the number of protons.
The mass number of an atom is the sum of protons and neutrons.✔✔It does not include electrons because their mass is negligible.
Isotopes are atoms of the same element with different numbers of neutrons.✔✔They have the same chemical properties but different atomic masses.
An ionic bond is formed when electrons are transferred from one atom to another.✔✔It usually occurs between metals and nonmetals.
A covalent bond involves the sharing of electrons between atoms.✔✔It typically occurs between nonmetal atoms.
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A polar covalent bond occurs when electrons are shared unequally.✔✔This creates partial positive and negative charges on the atoms.
The pH scale measures the concentration of hydrogen ions in a solution.✔✔A pH below 7 is acidic, and a pH above 7 is basic.
An acid releases hydrogen ions (H⁺) in water.✔✔A base accepts hydrogen ions or releases hydroxide ions (OH⁻).
The law of conservation of mass states that matter cannot be created or destroyed.✔✔The total mass of reactants equals the total mass of products in a chemical reaction.
A catalyst speeds up a chemical reaction without being consumed.✔✔It lowers the activation energy required for the reaction.
The periodic table arranges elements in order of increasing atomic number.✔✔Elements in the same group have similar chemical properties.
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Electronegativity measures an atom’s ability to attract electrons in a bond.✔✔Fluorine has the highest electronegativity of all elements.
An oxidation reaction involves the loss of electrons.✔✔Reduction involves the gain of electrons.
A molecule of water is held together by polar covalent bonds.✔✔Hydrogen bonding between water molecules gives it unique properties like high boiling point.
The molar mass of a compound is the sum of the atomic masses of its elements.✔✔It is measured in grams per mole (g/mol).
A chemical reaction where a substance reacts with oxygen to produce heat and light is called combustion.✔✔Combustion often produces carbon dioxide and water.
Avogadro’s number is 6.022 × 10²³.
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