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Questions and Answers
What is the molar mass of a compound composed of two nitrogen atoms and four oxygen atoms ($N_2O_4$)? (Molar mass of N = 14.01 g/mol, O = 16.00 g/mol)
What is the molar mass of a compound composed of two nitrogen atoms and four oxygen atoms ($N_2O_4$)? (Molar mass of N = 14.01 g/mol, O = 16.00 g/mol)
- 30.01 g/mol
- 46.01 g/mol
- 92.02 g/mol (correct)
- 76.01 g/mol
How many grams of NaCl (molar mass = 58.44 g/mol) are needed to have 2.5 moles?
How many grams of NaCl (molar mass = 58.44 g/mol) are needed to have 2.5 moles?
- 116.88 grams
- 146.10 grams (correct)
- 23.38 grams
- 29.22 grams
How many moles are present in 11.2 liters of $O_2$ gas at STP?
How many moles are present in 11.2 liters of $O_2$ gas at STP?
- 0.5 moles (correct)
- 1.0 moles
- 2.0 moles
- 1.5 moles
If a reaction requires 0.25 moles of $H_2SO_4$ (molar mass = 98.08 g/mol), what mass of $H_2SO_4$ is needed?
If a reaction requires 0.25 moles of $H_2SO_4$ (molar mass = 98.08 g/mol), what mass of $H_2SO_4$ is needed?
How many molecules are there in 0.75 moles of $H_2O$?
How many molecules are there in 0.75 moles of $H_2O$?
You have a sample containing $1.2044 \times 10^{24}$ atoms of carbon. How many moles of carbon do you have?
You have a sample containing $1.2044 \times 10^{24}$ atoms of carbon. How many moles of carbon do you have?
What volume will 3.0 moles of nitrogen gas ($N_2$) occupy at standard temperature and pressure (STP)?
What volume will 3.0 moles of nitrogen gas ($N_2$) occupy at standard temperature and pressure (STP)?
If you have 44.0 grams of carbon dioxide ($CO_2$), how many moles do you have? (Molar mass of $CO_2$ is 44.0 g/mol)
If you have 44.0 grams of carbon dioxide ($CO_2$), how many moles do you have? (Molar mass of $CO_2$ is 44.0 g/mol)
A container holds 88 grams of $CO_2$ gas. How many molecules of $CO_2$ are present in the container (Molar mass of $CO_2$ = 44 g/mol)?
A container holds 88 grams of $CO_2$ gas. How many molecules of $CO_2$ are present in the container (Molar mass of $CO_2$ = 44 g/mol)?
What volume is occupied by 0.5 moles of hydrogen gas ($H_2$) at STP?
What volume is occupied by 0.5 moles of hydrogen gas ($H_2$) at STP?
Flashcards
What is a mole?
What is a mole?
The amount of a substance containing exactly 6.02214076 × 10^23 entities.
What is Avogadro's Number?
What is Avogadro's Number?
6.02214076 × 10^23, the number of entities (atoms, molecules, etc.) in one mole.
What is molar mass?
What is molar mass?
The mass of one mole of a substance, expressed in grams per mole (g/mol).
How to find a compound's molar mass?
How to find a compound's molar mass?
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Moles to grams equation
Moles to grams equation
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Grams to moles equation
Grams to moles equation
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Moles to particles equation
Moles to particles equation
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Particles to moles equation
Particles to moles equation
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What is the molar volume of gas at STP?
What is the molar volume of gas at STP?
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What is stoichiometry?
What is stoichiometry?
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Study Notes
- The mole serves as a crucial unit in chemistry for expressing the quantity of a chemical substance.
- A mole is defined as precisely 6.02214076 × 10^23 entities, which can be atoms, molecules, ions, or other specified particles.
- Avogadro's number, commonly represented as NA, is the term for this value.
- The mole concept creates a connection between the atomic and macroscopic scales, enabling chemists to handle measurable amounts of substances while accounting for the number of atoms or molecules involved.
Determining Molar Mass
- Molar mass refers to the mass of one mole of a substance.
- For elements, the molar mass has the same numerical value as the element's atomic mass, expressed in atomic mass units (amu).
- The periodic table provides this value.
- The units for molar mass are grams per mole (g/mol).
- For compounds, the molar mass involves summing the molar masses of each atom in the chemical formula.
- As an example, water (H2O) has a molar mass of roughly (2 × 1.008 g/mol for H) + (1 × 16.00 g/mol for O) = 18.016 g/mol.
Mole Conversions
- Mole conversions commonly involve conversions between moles and grams, moles and the number of particles, and moles and volume, specifically for gases.
- Molar mass and Avogadro's number act as conversion factors in these processes.
Converting Moles to Grams
- Multiply the number of moles by the substance's molar mass to convert moles to grams:
- grams = moles × molar mass
Converting Grams to Moles
- Divide the mass in grams by the substance's molar mass to convert grams to moles:
- moles = grams / molar mass
Converting Moles to Number of Particles
- To convert moles to the number of particles, multiply the number of moles by Avogadro's number:
- number of particles = moles × Avogadro's number
Converting Number of Particles to Moles
- Divide the number of particles by Avogadro's number to convert the number of particles to moles:
- moles = number of particles / Avogadro's number
Molar Volume of Gases
- One mole of an ideal gas occupies about 22.4 liters at standard temperature and pressure (STP, which is 0 °C and 1 atm).
- At STP, this volume is known as the molar volume of a gas.
- Multiply the number of moles by 22.4 L/mol to convert moles of a gas at STP to volume:
- volume = moles × 22.4 L/mol (at STP)
- Divide the volume by 22.4 L/mol to convert the volume of a gas at STP to moles:
- moles = volume / 22.4 L/mol (at STP)
Applications of Moles and Molar Conversions
- Moles and molar conversions are crucial for stoichiometry, which studies the quantitative connections between reactants and products in chemical reactions.
- They facilitate calculations to determine the amounts of reactants needed to yield a particular amount of product, or the amount of product resulting from a given amount of reactant.
- Molar conversions play a vital role in preparing solutions of specific concentrations.
- Molarity (M), is used to express the concentration of a solution, and is defined as the number of moles of solute per liter of solution.
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Description
Understand the mole concept, a crucial unit in chemistry for expressing the amount of a chemical substance. Learn how one mole is defined by Avogadro's number. Explore how to determine molar mass for both elements and compounds using the periodic table.
