Questions and Answers
If 1.5 × 10²² molecules of a substance are present, how many moles does this represent?
0.025 moles
What is the relative molecular mass (Mᵣ) of carbon dioxide (CO₂)?
44
How many moles are there in 120 grams of calcium (Ca)?
3 moles
What is the volume, in liters, occupied by 2 moles of nitrogen gas (N₂) at room temperature?
Signup and view all the answers
Calculate the mass of 0.5 moles of sodium chloride (NaCl).
Signup and view all the answers
What is the volume, in cm³, of 0.25 moles of oxygen gas (O₂) at standard temperature and pressure (s.t.p.)?
Signup and view all the answers
Explain Avogadro's Law in your own words.
Signup and view all the answers
How many moles are present in 11,200 cm³ of methane (CH₄) at standard temperature and pressure?
Signup and view all the answers
What is the volume in cm³ of 1 mole of a gas at standard temperature and pressure?
Signup and view all the answers
How many moles are there in 336 cm³ of a gas at standard temperature and pressure?
Signup and view all the answers
How many atoms are there in 0.5 moles of aluminum?
Signup and view all the answers
What is the mass in grams of 2 moles of oxygen?
Signup and view all the answers
How many molecules are there in 0.25 moles of carbon dioxide?
Signup and view all the answers
What is the molar mass of ethane (C₂H₄)?
Signup and view all the answers
How many moles are there in 3 × 10²² atoms of silver?
Signup and view all the answers
What is the mass in grams of 3 × 10²² molecules of methane (CH₄)?
Signup and view all the answers
What is a mole and how is it used in chemistry?
Signup and view all the answers
How many atoms are present in 1 mole of CH₄ molecules?
Signup and view all the answers
Using Avogadro's number, how many molecules are there in 0.15 moles of CH₄?
Signup and view all the answers
Calculate the number of atoms in 0.15 moles of CH₄.
Signup and view all the answers
What is the molar mass of Carbon and Copper, and why is it relevant?
Signup and view all the answers
How many moles are represented by 1.5 × 10²² molecules of oxygen?
Signup and view all the answers
Explain the difference between the terms 'moles' and 'molecular weight'.
Signup and view all the answers
In the reaction H₂ + Br₂ → 2HBr, how many moles of HBr are produced from 1 mole of H₂?
Signup and view all the answers
Study Notes
The Mole
- A mole is the unit for the amount of a substance.
- 1 mole of Copper = 63.5 g, which has the same number of atoms as 12 g of Carbon.
- A mole of a substance contains as many particles (atoms, molecules, or ions) as there are atoms of ¹²C in 12g of ¹²C.
- Avogadro's Number (L) is 6 × 10²³ atoms, which is the number of atoms in 12g of ¹²C.
- 1 mole = 6 × 10²³ atoms or molecules or ions.
Moles in Chemical Formulas
- Moles are represented in chemical formulas, e.g., H₂ + Br₂ → 2HBr, where 1 mole of hydrogen reacts with 1 mole of bromine to form 2 moles of hydrogen bromide.
Calculations Involving Moles
- To find the number of molecules in a given number of moles, multiply the number of moles by 6 × 10²³ molecules.
- To convert the number of molecules to atoms, multiply by the number of atoms in each molecule.
- To find the number of moles in a given number of molecules, divide by 6 × 10²³ molecules.
Relative Atomic Mass (Aᵣ) and Relative Molecular Mass (Mᵣ)
- Aᵣ is the symbol for relative atomic mass and is used in association with atoms.
- It can be read from the periodic table, e.g., Mg has an Aᵣ of 24.31, which is rounded down to 24 for calculations.
- Mᵣ is the relative molecular mass and is associated with molecules, calculated by adding up the Aᵣ ’s of the individual atoms.
Converting Moles to Grams
- The formula to convert moles to grams is: moles × Mᵣ = Mass (in grams).
- This formula also works for Aᵣ.
Molar Volume of Gases
- Avogadro's Law states: Equal volumes of gases, under the same conditions of temperature and pressure, contain equal numbers of molecules.
- At standard temperature and pressure (s.t.p.), 1 mole = 22.4L = 22,400cm³.
- At room temperature and pressure, 1 mole = 24L = 24,000cm³.
Calculations Involving Moles, Volume, and Mass
- To find the number of moles in a given volume of gas, use the formula: moles = volume ÷ 22.4L (or 24L for room temperature and pressure).
- To find the mass in grams, use the formula: moles × Mᵣ = Mass (in grams).
- To find the number of atoms or molecules, use the formulas: moles × 6 × 10²³ atoms (or molecules) or mass ÷ Mᵣ.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the concept of moles, a unit of measurement for the amount of a substance, and how it applies to atoms and molecules of different elements like copper and carbon.
