Chemistry: Chemical Reactions & Stoichiometry Flashcards
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What does the Law of Conservation of Mass state?
Answer: Mass is conserved in a chemical reaction.
The Law of Conservation of Mass states that in any closed system, the total mass of the reactants before a chemical reaction must equal the total mass of the products after the reaction. This means that mass cannot be created or destroyed, only rearranged, during a chemical change. It is a fundamental principle in chemistry and physics.
What is stoichiometry used for in chemical reactions?
Answer: To calculate the amounts of reactants and products.
Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It uses balanced chemical equations to determine the precise amounts (moles, mass, volume) of substances consumed or produced. This allows chemists to predict yields and optimize reaction conditions.
What is the molar ratio in a balanced chemical equation?
Answer: The ratio of moles of reactants to moles of products.
In a balanced chemical equation, the coefficients in front of each chemical formula represent the molar ratio. This ratio indicates the relative number of moles of each reactant consumed and each product formed during the reaction. It is crucial for stoichiometric calculations, allowing conversion between the amounts of different substances in a reaction.
What is the limiting reagent in a chemical reaction?
Answer: The reactant that is used up first.
The limiting reagent (or limiting reactant) is the substance that is completely consumed first in a chemical reaction. Its quantity determines the maximum amount of product that can be formed, as the reaction stops once it runs out. All other reactants are considered to be in excess.
What is the mole concept used for in stoichiometry?
Answer: To convert between mass, volume, and number of particles in a reaction.
The mole concept provides a bridge between the macroscopic world (mass, volume) and the microscopic world (number of atoms/molecules). In stoichiometry, it allows chemists to convert between grams, liters (for gases), and the number of moles of a substance, which is essential for relating the quantities of different substances in a balanced chemical equation.
What is the purpose of balancing a chemical equation?
Answer: To ensure the correct stoichiometric relationship between reactants and products.
Balancing a chemical equation ensures that the law of conservation of mass is upheld, meaning atoms are neither created nor destroyed. By adjusting coefficients, we establish the correct molar ratios between reactants and products. This accurate ratio is fundamental for all stoichiometric calculations, allowing precise predictions of reaction outcomes.
What is a combustion reaction?
Answer: A reaction that produces heat and light, usually with oxygen.
A combustion reaction is a high-temperature exothermic redox reaction, typically involving a fuel and an oxidant, usually atmospheric oxygen. It is characterized by the rapid release of energy in the form of heat and light. Common examples include the burning of hydrocarbons, producing carbon dioxide and water.
What is the difference between empirical and molecular formulas?
Answer: Empirical formulas show the simplest ratio, while molecular formulas show the actual number of atoms.
An empirical formula represents the simplest whole-number ratio of atoms of each element in a compound. In contrast, a molecular formula indicates the actual number of atoms of each element present in a single molecule. For example, the empirical formula for glucose is CH₂O, while its molecular formula is C₆H₁₂O₆.
What is the significance of stoichiometry in determining the yield of a reaction?
Answer: It helps calculate the theoretical yield and compare it with the actual yield.
Stoichiometry is crucial for determining the theoretical yield, which is the maximum amount of product that can be formed from a given amount of reactants based on the balanced chemical equation. By comparing this theoretical yield to the actual yield obtained experimentally, chemists can calculate the percent yield and assess the efficiency of a reaction.