A-Level Chemistry Flashcards

Natalie_B
Flashcards by , created over 3 years ago

A-Level Chemistry Flashcards

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Natalie_B
Created by Natalie_B over 3 years ago
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Question Answer
Define the parts of a chemical formula. For example: 31bc8b20-cb12-4866-9e1e-5144de53511b.jpg (image/jpg) 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. 7b25970a-8d9e-45ec-8734-2b332777c64f.png (image/png)
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. 1073e300-8a0b-46ac-8870-9d5156d2a32f.jpg (image/jpg)
Draw the flowchart for determining Intermolecular Forces. 0d76a8bc-54e8-458d-9f92-ffad0d149cb6.jpg (image/jpg)
Define the strength of each type of Intermolecular Forces as well as the nature of the attraction. c7090173-1802-40f8-9eaf-8598595cd660.jpg (image/jpg)
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? 39e44c0e-42f3-4c33-96c0-6783fd6a8d74.PNG (image/PNG)
How do you calculate the molarity (concentration) of a solution? b1d1af55-87a9-49d6-8e58-77c158356a87.jpg (image/jpg)
Label the reaction types: efeafe47-f474-4cf2-bbb6-aa30e268bb0c.jpg (image/jpg) 4a310f3c-5698-458b-9ae9-a167c2c1b11c.png (image/png)
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