Chemistry chapter 1: stoichoimetry Flashcards
Define Avogadro’s number.
A: Avogadro’s number is
6.022×10^23, representing the number of atoms, molecules, ions or particles in one mole of a substance.
What is a mole in chemistry?
A: A mole is the amount of substance that contains exactly
6.022×10^23
entities (atoms, molecules, ions, etc.), known as Avogadro’s number.
And it is the number of atomic, formula and molecular mass expressed in grams.
Why is chemistry considered a quantitative science, and how does it impact daily life?
A: Chemistry is considered a quantitative science because it involves measurements, calculations, and precise quantities (moles, mass, volume, etc.) used to predict outcomes. It impacts daily life in areas like medicine, food, environment, and industrial processes.
How is the mole concept related to Avogadro’s number?
A: One mole of any substance contains
6.022×10^23 particles, such as atoms, molecules, or ions, which is Avogadro’s number.
How do you calculate the number of atoms, molecules, moles, ions, protons, neutrons, or electrons?
A: Use the formula:
Number of particles=moles×Avogadro’s number
For protons, neutrons, and electrons, use atomic number and mass number to find the counts.
How do you calculate interacting moles and representative particles from a balanced chemical equation?
A: Use the mole ratio from the balanced equation to convert between moles of reactants and products.
How do you calculate the masses and volumes of gases at STP and RTP?
A: Use the molar volume of gas: 22.4 L at STP and 24 L at RTP. The formula is:
Volume=Moles×Molar volume.
How do you calculate the percentage by mass of elements in a compound?
A: Use the formula:
Percentage by mass= Mass of (element in 1 mole of compound/
Molar mass of compound)×100.
How do you solve stoichiometric problems using mole ratios?
A: Use the mole ratio from the balanced equation as a conversion factor to find the moles of reactants or products.
How do you calculate the percentage of water of crystallisation in hydrated salts?
A: Use the formula:
Percentage of water= (Mass of water/
Mass of hydrated salt)×100.
How do you deduce the empirical and molecular formula of a compound?
A: Find the simplest whole number ratio of atoms (empirical formula).
Use the molar mass and empirical formula to find the molecular formula:
Molecular formula= n(Empirical formula)
How do you determine the limiting reagent in a chemical reaction?
A: The limiting reagent is the reactant that is consumed first, limiting the amount of product formed. Compare the mole ratios of reactants to the balanced equation to determine this.
How do you calculate the maximum amount of product and the amount of excess reagent left unreacted?
A: Use the limiting reagent to calculate the moles of product.
Subtract the moles of excess reagent used from the initial moles to find the unreacted amount.
What is the difference between theoretical yield, actual yield, and percentage yield?
A:
- Theoretical yield is the maximum product calculated from the limiting reagent.
- Actual yield is the product obtained in practice.
- Percentage yield= (Actual yield/Theoretical yield)×100.
How many molecules are present in 2 moles of water (H₂O)?
A:
Use Avogadro’s number:
1 mole=6.022×10^23 molecules.
Multiply by the number of moles:
2 moles of H₂O×6.022×10^23 =1.204×10^24 molecules.