Practice Problem: Gibbs Free Energy

Given Question: The reaction given above is accompanied by the Enthalpy of the reaction (H) and the entropy (S). Determine the change in Gibbs Free energy (G) and if the reaction is spontaneous or not. If the reaction isn’t spontaneous, calculate the temperature in which it will be.  Start off by listing what we know, […]

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Determining the Molar Solubility of Iron (II) Hydroxide

Given Question: Calculate the molar solubility of Fe(OH)2 (Ksp=4.87*10^-7).  Tutor’s Note: The Ksp radical that’s written down comes in later, I got confuzzled by my own notes! Happens to all of us. Sorry students 🙂  Step 1: Write out the reaction equation with all ions. Make sure it’s balanced! We’ll use this in the next step with […]

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Determining Precipitate Yield (g) in Aqueous Solution

Given Question: Given the reaction: K3(PO4)+ Ni(SO4)→ K3(SO4)(aq)+Ni(PO4)(s), with 100.0 ml of K3PO4 and 200.0 ml of NiSO4 under standard conditions, how many grams of precipitate form?  Step 1: Determine the limiting reactant and the precipitate.  In order to determine the limiting reactant, one must convert all reactants to moles (mol). In this case, we can […]

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Calculating the pH of a Buffer System

The point of this problem is to correctly calculate the pH of a buffer system using formonitrile, or hydrogen cyanide. Here, we use the dissociation constant and the Henderson-Hasselbach equation. Given Problem: Calculate the pH of a buffer that’s .250 M HCN (kª= 4.9*10^-10) and 0.170 M KCN.  2. This is to remind us of the […]

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Titration of Strong Acid With Strong Base

The goal of this example is to help students become fluent in calculating pH/pOH of a solution during a titration of a strong acid (HCl) and a strong base (NaOH). This problem includes calculations for titrations of increasing volumes. Given Problem: Calculate the pH of a titration of 25.0 mL of HCl (.100 M) with […]

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Calculating Acid:Buffer Ratio using H-H Equation

Given Question: Which acid would you combine with its Na (sodium) sat to create a buffer with a pH of 7.35. What ratio of a buffer to acid is needed? There are 3 potential buffers provided to choose from. 1. First, we choose which buffer is the best acid to choose to obtain the desired […]

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VSEPR Theory Examples (chem.purdue)

Given Problem: Draw the Lewis dot structures, identify the molecular geometry, and give the bond angle for the following compounds: BeF2 BCl3 SI6 1. BeF2: The first step is to draw the Lewis dot structure. This can be done by identifying how many bonding groups are involved.  A bonding group, counts as 1 lone electron, an electron pair, […]

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Balancing Equations (Chem.libretext example)

The point of this exercise is to practice balancing reactions. Many students get overwhelmed when they face having to balance equation usually because it’s hard to determine where to start. Given Problem: Lead (IV) Hydroxide and sulfuric acid react as: Pb(OH)4+H2SO4→ Pb(SO4)2+H2O Balance the equation: 1. The first step to balancing a chemical reaction is to identify […]

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Determining the Density of a Face-Centered Aluminum Cell

Crystals come in unique shapes, but all usually have an organized, repeating structure known as a lattice. For more information about metal lattices check out: https://www.seas.upenn.edu/~chem101/sschem/metallicsolids.html  Given Problem: An aluminum crystal has a face-centered unit cell. An aluminum atom has a radius of 143 picometers. What is the density of the solid crystal aluminum in g/cm³?  […]

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