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 … Continue reading Calculating Acid:Buffer Ratio using H-H Equation
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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, … Continue reading VSEPR Theory Examples (chem.purdue)
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 … Continue reading Balancing Equations (Chem.libretext example)
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? … Continue reading Determining the Density of a Face-Centered Aluminum Cell
Gas Volume Stoichiometry Problem
Given Problem: Methanol (CH3OH) can be synthesized as: CO+2H2→CH3OH. What volume in liters of H2(g) is needed to make 35.7 grams of CH3OH? 1. We are given the temperature at 355 K and the pressure is 738 mmHg. 2. First, you must convert the target mass of CH3OH to moles. To do this, you use the molar mass … Continue reading Gas Volume Stoichiometry Problem
Calculating Percent Yield
Given Question: 155.8 Kg of SiO2 reacts with 78.3 Kg of Carbon to produce 66.1 Kg of silicon. What is the percent yield of the reaction? 1. The first step is to convert your given masses into moles. This way, you can see which reactant is in excess and which one is limiting. A good … Continue reading Calculating Percent Yield
Calculating Final Temperature of Heated Al in H2O (Example)
Given Problem: A block of Aluminum has a mass of 32.5 grams and is at 45.8° C. It's placed in 105.3 grams of water at 15.4° C. What's the final temperature for both the aluminum and water? 1. These are the equations we're going to use. Because we have two equations for q, we can substitute … Continue reading Calculating Final Temperature of Heated Al in H2O (Example)
Calculating Temperature Change Using Q=mCsΔT
This problem is designed to get you comfortable working with the equation given, and is good because it gets you to think of Q in terms of joules. Given Problem: 25 grams of gold (Au) is initially at 27°C. It absorbs 2.35 kJ of heat. What is the final temperature of the gold? The specific heat … Continue reading Calculating Temperature Change Using Q=mCsΔT
Finding Wavelength of Light (nm) Using Frequency (Hz)
The point of this problem is to be able to use the c=λν to find the wavelength of light. This problem could also be structured to find the frequency of the light using just the wavelength. 1. The equation we're working with has two values already entered in it. The speed of light (3.00*10^8 m/s) … Continue reading Finding Wavelength of Light (nm) Using Frequency (Hz)
Determining Empirical Formula (Example)
The outcome of this problem is to understand how to find the empirical formula of the unknown reactant in this combustion reaction. Given Problem: The combustion reaction X+O2→ CO2 + H2O contains 1.29 grams of X reactant, where X is an unknown compound containing C,H, & O. The reaction yields 1.13 grams of H2O and 2.086 … Continue reading Determining Empirical Formula (Example)
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