Mole-gram conversions

Such problems as this one involve many steps or conversions. Try to break the problem into simpler ones involving fewer steps or conversions. It may also help to remember that solving a stoichiometry problem involves three steps (1) converting to moles, (2) converting between moles, and (3) converting from moles. Use molarities and molar masses to carry out volume-mole conversions and gram-mole conversions, respectively, and stoichiometric factors to carry out mole-mole conversions. The stoichiometric factors are constructed from a balanced chemical equation. 

For a redox reaction in an electrochemical cell the decrease in free enthalpy (- AG) is in accordance with the energy delivered by the transfer of electrons through an external circuit if this takes place in a reversible way, i.e., at a rate slow enough to allow complete attainment of equilibrium, the conversion of 1 gram mole will deliver an electrical energy of - AG = z FE. In total cell reaction mred, + n ox2 m ox, + nred2, where m81 = nS2 electrons are transfered (<5, and S2 represent the respective valence differences of the two redox systems), we have... 

Be familiar with the basic calculations involved in each experiment. Review the appropriate equations given on the AP Exam. Know which ones may be useful in each experiment. Also, become familiar with simple calculations that might be used in each experiment. These include calculations of moles from grams, temperature conversions, and so on. 

First, find out how many moles of Cl2 are in 25.0 g of Cl2. This gram-to-mole conversion is done in the usual way, using the molar mass of Cl2 (70.9 g/mol) as the conversion factor ... 

To calculate the molarity of the KMn04 solution, we need to find the number of moles of KMn04 present in the 22.35 mL of solution used for titration. We do this by first calculating the number of moles of oxalic acid that react with the permanganate ion, using a gram-to-mole conversion with the molar mass of H2C2O4 as the conversion factor ... 

Other convenient units for pointwise permeability are g-moles/ cm -sec-atm/cm., applicable to both liquids and gases. The conversion for gaseous pointwise permeabihty utilizes the value of 22,414 cm (STP) per gram-mole, and a value of 76 cm Hg/atm. Thus... 

A batch recycle reactor (Fig. 12-1), operated differentially and used for the gas-phase photolysis of acetone, has a volume of 62.8 cm, while the total volume of the system is 6,620 axr. Runs at 97°C and 870 mm Hg pressure were made at different initial concentrations of acetone in helium. Typical data for conversion to C2H6 are as given below for varying initial concentrations (gram moles per liter). The products of photolysis are primarily CjHe and CO, according to the overall reaction... 

First, determine the mass of NaCl to add to a 1.0-L container. The 0.15M solution must contain 0.15 moles of NaCl per liter of solution. You will need to use the molarity of the solution (0.15 mol NaCl/L solution) as a conversion factor to get from molarity to number of moles of NaCl. You win then use the molar mass of NaCl as a conversion factor to change moles of NaCl to grams of NaCl. To find the molar mass of NaCl (58.5 g/mol), add the atomic masses of Na and Cl, and apply the unit grams/mole to the sum. 

Determine that the molar mass of KCl is 74.6 g/mol by adding the atomic masses of K and Cl and applying the unit grams/mole to the srun. The conversion factor that must be used to convert from grams to moles of KCl is 1 mol KCl/74.6 g KCl. 

Thus the conversion factor that converts back and forth between grams moles of iron(lll) sulfate is... 

The atomic mass of C is 12.01 amu therefore, 1 mole C = 12.01 g C. This equality provides the needed gram-to-mole conversion factor. 

Figure 3.8 Summary of the mass-mole-number relationships in a chemical reaction. The amount of one substance in a reaotion is related to that of any other. Quantities are expressed in terms of grams, moles, or number of entities (atoms, molecules, or formula units). Start at any box in the diagram (known) and move to any other box (unknown) by using the information on the arrows as conversion factors. As an example, if you know the mass (in g) of A and want to know the number of molecules of B, the path involves three calculation steps ...

At the end of the dimensionless area calculation, absolute permeability and pressure values are assigned in terms of a conversion (or divisor factor) for a specified membrane thickness, also as in Appendix 4. The area so calculated in cm" is placed on the basis of 1 gram-mole per second of feedstream. 

Notice how dimensional analysis (Section 1.6) provides a straightforward route from grams to numbers of atoms. The molar mass and Avogadro s number are used as conversion factors to convert grams---> moles-----> atoms. 

Also notice that molarity, as expressed in Equations 16.2 and 16.3, includes one unit that is particulate (moles, number of particles) and one unit that is macroscopic (volume, which can be measured). To be practical—to actually work with molarity in the laboratory—you must convert moles to a macroscopic unit, grams. The conversion factor, as you probably know from many uses by now, is molar mass in grams per mole. 

To find molarity from its definition (Equation 16.2), you need to know the volume of solution, which is given, and the moles of NaOH. Grams are given. The grams-to-moles conversion must be made before you can use the defining equation. How many moles of NaOH are in the solution ... 

Gram-to-mole conversions require the molar mass of the given substance and the mole ratio. 

Given the amount in mol of H2O, you need to get the mass of CgHj20g in grams. Two conversion factors are needed—the mole ratio of CgHj20g to H2O and the molar mass of CgHj20g. 

Gram-to-Mole Conversions This is a solution plan for problems in which the given quantity is expressed in grams, and the unknown quantity is expressed in moles. 

This is a gram-to-mole conversion. Grams of KCIO3 must be converted to moles before we can use the mole ratio from the equation to get moles of oxygen. The formula weight of KCIO3 is 122.548 g/mol. 

If Va is the volume of gas A in cubic centimeters at t°C and Pa, Ma is the gram-mole volume of A decided upon, expressed as cubic centimeters, ds is the density of the liquid S used to absorb the gas, and Mg is the molecular weight of S (taken as the formula weight), then the mole ratio Xa is given by Va and Na then equals Xa/(1 + Xa). The Xa value relates to the temperature and pressure of measurement and to the gram-mole volume chosen for these conditions. For arguments on a molecular basis, I can find no useful purpose in the conversion of the Ostwald coefficient into the Bunsen coefficient. 

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