Study Guide: Moles & Mole Road

1. Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). 2. - **Gram atomic mass** is the mass of one mole of atoms of an element, expressed in grams per mole. - **Gram formula mass** is the mass of one mole of a compound's formula, summing the atomic masses of all atoms in the formula, expressed in grams per mole. - **Gram molecular mass** refers to the mass of one mole of a molecular substance, calculated by summing the atomic masses of its constituent atoms. 3. If the molar mass is 100.0 grams and you have 100.0 grams, you have 1 mole of the substance. 4. A mole is a unit of measurement that represents 6.022 x 10²³ particles (atoms, molecules, ions, etc.) of a substance. 5. The gram atomic mass of carbon-12 is 12.01 g/mol, while for carbon-13 it is about 13.00 g/mol. 6. If you have a mole of atoms, you would have 6.022 x 10²³ atoms. 7. You would have 6.022 x 10²³ molecules for a mole of molecules, 6.022 x 10²³ atoms for a mole of atoms, 6.022 x 10²³ ions for a mole of ions, and 6.022 x 10²³ formula units for a mole of formula units. 8. The formula for ammonium hydroxide is NH₄OH. 9. The formula NH₄OH is classified as a molecular formula because it represents the composition of the molecule. 10. A **formula unit** is the lowest whole number ratio of ions in an ionic compound. Example: NaCl (sodium chloride). A **molecular formula** represents the actual number of atoms in a molecule of a covalent compound. Example: H₂O (water). 11. A type of bond (ionic vs covalent) can classify a formula as molecular (covalent) or ionic (ionic). For instance, H₂O is molecular, while NaCl is ionic. 12. A substance is called a “salt” if it is composed of a cation from a base and an anion from an acid, usually resulting from the neutralization reaction between an acid and a base. 13. The molar mass of ammonium hydroxide (NH₄OH) is approximately 35.05 g/mol. This is calculated as: 14.01 (N) + 4.00 (H) + 16.00 (O) + 1.01 (H) = 35.05 g/mol. 14. Avogadro’s number is approximately 6.022 x 10²³. So, multiplying by 3 gives 1.80666 x 10²⁴. 15. Dividing Avogadro’s number by 3 gives approximately 2.00733 x 10²². 16. In one mole, there would be 6.022 x 10²³ molecules. 17. In 18.02 grams of water, you would have approximately 6.022 x 10²³ molecules (1 mole of water). 18. In 18.02 grams of water (H₂O), you would have 1 mole of oxygen atoms, which equals 6.022 x 10²³ oxygen atoms. 19. In 18.02 grams of water, you would have 2 moles of hydrogen atoms, which equals 2 * 6.022 x 10²³ = 1.2044 x 10²⁴ hydrogen atoms. 20. For 36.04 grams of water, you would have 2 moles (12.044 x 10²³ molecules), and for 180.2 grams of water, you would have 10 moles (6.022 x 10²⁴ molecules). 21. In 36.04 grams of water, you would have 2 moles of water; in 72.08 grams, you would have 4 moles of water. 22. In half a mole, you would have approximately 3.011 x 10²³ atoms (half of Avogadro’s number). 23. In 5 moles of atoms, you would have 5 * 6.022 x 10²³ = 3.011 x 10²⁴ atoms. 24. The mole is measured by mass rather than by counting each particle because particles are extremely small and measuring mass is a more practical and convenient method for quantifying substances. 25. A representative particle can be an atom, molecule, formula unit, or ion, depending on the type of substance being considered. 26. If you have half a mole, you would have approximately 3.011 x 10²³ atoms. 27. If you have one quarter mole, you would have approximately 1.506 x 10²³ molecules. 28. In 10 moles, you would have 10 * 6.022 x 10²³ = 6.022 x 10²⁴ formula units. 29. In 5 moles, you would have 5 * 6.022 x 10²³ = 3.011 x 10²⁴ ions. 30. STP stands for Standard Temperature and Pressure. 31. Conditions for STP are 0 degrees Celsius (273.15 K) and 1 atmosphere (atm) pressure. 32. One mole of oxygen gas (O₂) has a mass of 32.00 grams, comprises 2 atoms, and includes 6.022 x 10²³ molecules due to being diatomic. 33. One mole of oxygen gas at STP occupies 22.4 liters. 34. One mole of oxygen gas at STP contains 6.022 x 10²³ molecules. 35. The significance of 22.4 liters is that it is the volume occupied by one mole of any gas at STP. 36. The value of 22.4 liters is used in problems involving gas stoichiometry or converting between moles of a gas and its volume at STP. 37. In 32.07 grams of sulfur, there are approximately 1 mole (in fact, 1 mole of sulfur atoms contains about 6.022 x 10²³ atoms). 38. The seven diatomic elements are hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), chlorine (Cl₂), bromine (Br₂), and iodine (I₂). 39. The molar mass of chlorine gas (Cl₂) is approximately 70.90 g/mol, and for nitrogen gas (N₂) it is approximately 28.02 g/mol.