Elements and Compounds in Chemical Reactions

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What is an element?

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An element is a pure substance that cannot be broken down into simpler substances by chemical means. Examples include hydrogen (H), oxygen (O), and gold (Au).

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What is a compound?

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A compound is a substance formed when two or more elements chemically bond together. Examples include water (H2O) and carbon dioxide (CO2).

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What is a chemical reaction?

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A chemical reaction is a process that involves the rearrangement of the molecular or ionic structure of a substance, resulting in the formation of new substances.

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What does pH measure?

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pH measures the acidity or basicity of a solution. A pH less than 7 indicates an acid, a pH of 7 indicates neutrality, and a pH greater than 7 indicates a base.

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What is the law of conservation of mass?

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The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction; it remains constant.

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What is a balanced chemical equation?

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A balanced chemical equation has equal numbers of each type of atom on both sides of the equation, reflecting the conservation of mass.

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What is an acid?

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An acid is a substance that donates protons (H+) in a solution and has a pH less than 7. Examples include hydrochloric acid (HCl) and sulfuric acid (H2SO4).

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What is a base?

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A base is a substance that accepts protons (H+) or donates hydroxide ions (OH-) in a solution and has a pH greater than 7. Examples include sodium hydroxide (NaOH) and ammonia (NH3).

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What is the role of oxygen in cellular respiration?

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Oxygen is used in cellular respiration to help break down glucose, producing energy, carbon dioxide, and water.

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What is the formula for calculating the number of moles?

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The number of moles can be calculated using the formula: Moles = Mass (g) / Molar Mass (g/mol).