# Stoichiometry concept questions and answers

1. Q: What is stoichiometry in chemistry? A: Stoichiometry is a branch of chemistry that deals with the quantitative relationships that exist among the reactants and products in chemical reactions.

2. Q: How are stoichiometric coefficients used in a balanced chemical equation? A: Stoichiometric coefficients are the numbers placed in front of compounds in a chemical reaction to balance it. They represent the number of moles of a substance that participate in the reaction.
3. Q: What is a mole in chemistry? A: A mole is a unit of measurement in chemistry. It is used to express amounts of a chemical substance. One mole of any substance contains Avogadro’s number (approximately 6.022 x 10^23) of elementary entities (atoms, molecules, ions, etc.).
4. Q: What is Avogadro’s number? A: Avogadro’s number, also known as Avogadro’s constant, is the number of atoms in exactly 12 grams of carbon-12. It is approximately 6.022 x 10^23 entities per mole.
5. Q: What is a limiting reactant? A: The limiting reactant is the substance that is completely consumed when a chemical reaction is carried out. It determines the maximum amount of product that can be formed.
6. Q: What is the excess reactant? A: The excess reactant is the substance that is not used up completely in a reaction. After the reaction is complete, some amount of the excess reactant is left over.
7. Q: How do you calculate the theoretical yield of a reaction? A: The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. It is calculated using the balanced chemical equation and the amount of the limiting reactant.
8. Q: What is the difference between actual yield and theoretical yield? A: The actual yield is the amount of product that is actually produced when the chemical reaction is carried out in an experiment. The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. The actual yield is usually less than the theoretical yield due to losses during the experiment and other factors.
9. Q: What is the percent yield of a reaction? A: The percent yield is the ratio of the actual yield to the theoretical yield, multiplied by 100%. It is a measure of the efficiency of a reaction.
10. Q: What is a mole ratio? A: A mole ratio is the ratio of moles of one substance to the moles of another substance in a balanced chemical equation.
11. Q: How is stoichiometry used to determine the amount of reactants needed or product formed in a reaction? A: Stoichiometry is used to determine the amount of reactants needed or product formed in a reaction by using the balanced chemical equation, which provides the mole ratios of reactants and products.
12. Q: How do you determine the empirical formula of a compound? A: The empirical formula of a compound can be determined from the percent composition of each element in the compound. It shows the simplest whole-number ratio of atoms in the compound.
13. Q: What is the difference between the empirical formula and the molecular formula of a compound? A: The empirical formula shows the simplest whole-number ratio of atoms in a compound, while the molecular formula shows the actual number of atoms of each element in a molecule of the compound.
14. Q: How do you calculate molar mass? A: The molar mass of a substance is calculated by adding up the atomic masses of each atom in its chemical formula. The atomic masses can be found on the periodic table.
15. Q: What is a balanced chemical equation? A: A balanced chemical equation is an equation that shows the reactants and products in a chemical reaction. It is balanced when the number of atoms of each element is the same on both sides of the equation, adhering to the Law of Conservation of Mass.
16. Q: What is the stoichiometric equivalent of a reaction? A: The stoichiometric equivalent of a reaction refers to the molar ratios of reactants and products in a balanced chemical equation. These ratios provide the relationship between the amounts of reactants consumed and products formed.
17. Q: How do you use stoichiometry to perform dilution calculations? A: In a dilution, the amount of solute remains constant, while the amount of solvent is increased. The relationship between the initial and final concentrations and volumes of the solution is given by the equation C1V1 = C2V2, where C is the concentration and V is the volume.
18. Q: How does a stoichiometrically balanced equation reflect the law of conservation of mass? A: A stoichiometrically balanced equation reflects the law of conservation of mass by showing that the number of atoms of each element in the reactants is equal to the number of atoms of the same element in the products.
19. Q: How do you use stoichiometry to perform solution concentration calculations? A: Stoichiometry can be used to calculate solution concentrations by using the molar ratios in a balanced chemical reaction. Given the concentration of one substance, one can calculate the concentration of another substance involved in the reaction.
20. Q: How can stoichiometry be applied to real-world situations? A: Stoichiometry can be applied in many real-world situations such as cooking, where recipes can be thought of as chemical reactions, and in environmental science, where it is used to understand the chemistry of the ozone layer, acid rain, etc. It is also used in industry to optimize the production of various goods and materials.

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