4590518
| Questão | Responda |
| Define the parts of a chemical formula. For example: | Left of Arrow = Reactants Right of Arrow = Products Subscripts = Number of that type of atom (e.g. In CH4, there is 1 Carbon atom and 4 Hydrogen atoms) Coefficients = Number of moles (No coefficient = 1 mole of substance) |
| What are Lewis Structures used for? Show the Lewis Structure for Sodium Chloride (NaCl). | Lewis Structures are cross and dot diagrams which allow us to visualise the number of valence electrons of each atom in order to predict how they bond. |
| What is VSEPR modelling? List the main expressions. | Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. |
| Draw the flowchart for determining Intermolecular Forces. | |
| Define the strength of each type of Intermolecular Forces as well as the nature of the attraction. | |
| What is Avogadro's Constant? | Avogadro's Constant is the number of atoms in a mole. There are 6.022 x 10^23 atoms per mole. |
| How do you convert the number of atoms in a substance to moles and visa versa? | Divide the number of atoms by Avogadro's Constant (6.022 x 10^23) to give the number of moles. Multiply the number of moles by Avogadro's Constant to find the number of atoms. |
| How do you convert moles to grams and visa versa? | Multiple moles by molecular mass to convert to grams. Divide grams by molecular mass to convert to moles. |
| How do you find the amount of moles in a sample? | |
| How do you calculate the molarity (concentration) of a solution? | |
| Label the reaction types: | |
| When determining oxidation states, which elements/elemental groups do we generally trust and what are their oxidation numbers? | Trust: Oxygen = -2 Hydrogen = +1 Group 1 & 2 Metals = +1 & +2 Halogens (F, Cl, Br, I, At) = -1 If in pure elemental form = 0 |
| Redox Equations First step | Assign oxidation states. |
| Redox Equations Second step | Divide into half-reactions. e.g. Reduction and Oxidation. |
| Redox Equations Third Step | Balance each half-reaction. - Balance elements other than H and O. - Balance O by adding H2O as needed. - Balance H by adding H+ as needed. - Balance the charge by adding e-'s. |
| Redox Equations Fourth Step | Balance Half-Reactions. - Multiply all oxidation half-reaction by number of electrons in the reduction half-reaction. - Multiple all reduction half-reaction by number of electrons in the oxidation half-reaction. |
| Redox Equations Final Step | Add the two half-reactions together again, cancelling out any substances occurring on both sides and electrons. |
| What goes where on the pH scale? | 1 = Acid (H+) 7 = Neutral (H2O) 14 = Alkaline (OH) |
| How do you calculate the pH of an acid and an alkaline? | Acid pH = -log10(Molarity) Alkaline pOH = -log10(Molarity) = x pH = 14 - x |
| What is the law of the conservation of energy? (First law of thermodynamics) | Energy can neither be created nor destroyed; rather, it transforms from one form to another. The law of conservation of energy states that the total energy of an isolated system remains constant—it is said to be conserved over time. |
| When considering the energy of reactions, what is meant by the 'system' and what is meant by the 'surroundings'? | System = reactions & products Surroundings = container & everything beyond it. |
| Define: Endothermic Exothermic | Endothermic = system absorbs heat. Exothermic = system loses heat. En - Enter. Ex - Exit. |
| If the change in a system's internal energy, (U), is positive, is it endothermic or exothermic? Why? | It is endothermic as a positive value indicates the system has GAINED energy. So if a change in U is negative, it is exothermic as the negative value indicates a loss of energy from the system. |
| What is enthalpy? What is the basic enthalpy equation? | Enthalpy (H) accounts for heat flow in processes occurring at constant pressure. H = U + PV P = Pressure, V = Volume. |
| What does a change in enthalpy mean? Basic equation? | A change in enthalpy equals the heat gained or lost at constant pressure by the system. DH = DU + P(DV) D = Delta = Change/Variation DH+ = endothermic, DH- = exothermic |
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