Mole-mass

The approach followed in Chapter 3 to calculate mole-mass relations in reactions is readily applied to solution reactions represented by net ionic equations. 

Mole-mass, 55,70-72q Molecular formula A formula in which the number of atoms of each type in a molecule is indicated as a subscript after the symbol of the atom, 34,59-60 Molecular geometry The shape of a molecule, describing the relative positions of atoms, 175 193q electron pairs, 179t major features, 175-176 molecules with expanded octets, 181t molecules with unshared electron pairs, 181t... 

As with all calculations of chemical amounts, we must work with moles. Because grams are asked for, we must do a mole-mass conversion this requires the molar mass of the substance, which in turn requires that we know the chemical formula. 

The ideal gas equation can be combined with the mole-mass relation to find the molar mass of an unknown gas PV = nRT (ideal gas equation) and n — (mole-mass relation) if we know the pressure, volume, and temperature of a gas sample, we can use this information to calculate how many moles are... 

Whereas liquids and solids have well-defined densities, the density of a gas varies strongly with the conditions. To see this, we combine the ideal gas equation and the mole-mass relation and rearrange to obtain an equation for... 

The question asks for mass of NO. Information about ppm tells us how many moles of NO are present in one mole of exhaust gas. We can use the ideal gas equation to determine the total number of moles of gas emitted, use the ppm information to find moles of NO, and do a mole-mass conversion to get the required mass. 

Because we know we are dealing with a buffer solution made from a specific conjugate acid-base pair, we can work directly with the buffer equation. We need to calculate the ratio of concentrations of conjugate base and acid that will produce a buffer solution of the desired pH. Then we use mole-mass-volume relationships to translate the ratio into actual quantities. 

Ans. The quantities of two reactants (or products) arc given in the problem. They might be stated in any terms—moles, mass, etc.—but they must be given for the problem to be a limiting quantities problem. 

By application of EMMA Regehr and Regnier developed several assays for enzymes that produce (galactose oxidase and glucose oxidase) or consume (catalase) hydrogen peroxide. Unlabeled enzymes were determined in the femto-mole mass range, while detection limits of less than 10,000 molecules were reported for catalase [101]. 

This is a critical chapter in your study of chemistry. Our goal is to help you master the mole concept. You will learn about balancing equations and the mole/mass relationships (stoichiometry) inherent in these balanced equations. You will learn, given amounts of reactants, how to determine which one limits the amount of product formed. You will also learn how to determine the empirical and molecular formulas of compounds. All of these will depend on the mole concept. Make sure that you can use your calculator correctly. If you are unsure about setting up problems, refer back to Chapter 1 of this book and go through Section 1-4, on using the Unit Conversion Method. Review how to find atomic masses on the periodic table. Practice, Practice, Practice. 

The enthalpy change is calculated by dividing the calculated energy by the moles, mass, or some other designated quantity. 

Species variable mass mass molar cone./ molar mass mole mole/mass mass mass... 

Doing conversions Mole-mole, mole-particles, mole-volume, and mole-mass Figuring out what happens when one reagent runs out before the others Using percent yield to determine the efficiency of reactions... 

A problemsolving flowchart showing the use of mole-mole, mole-mass, mole-volume, and mole-particle conversion factors. 

In terms of units, Heir = KclR = (length2 mass-2 mole)(mass length-3)/(length-1) = mole mass "1, reciprocal molecular weight units if mass is expressed in grams, as is the case in practical concentration units. 

Carry out mole-to-mole, mass-to-mole, and mass-to-mass calculations for any two species involved in a chemical reaction, Example L.l. 

The theoretical yield of a reaction is the maximum amount (moles, mass, or volume) of product that can be obtained from a given amount of reactant. The amounts of products calculated from a given mass of reactant in Section L were all theoretical yields. 

We saw in Section 3.3 that the coefficients in a balanced equation tell the numbers of moles of substances in a reaction. In actual laboratory work, though, it s necessary to convert between moles and mass to be sure that the correct amounts of reactants are used. In referring to these mole-mass relationships, we use the word stoichiometry (stoy-key-ahm-uh-tree from the Greek stoicheion, "element," and metron, "measure"). Let s look again at the reaction of ethylene with HC1 to see how stoichiometric relationships are used. 

Some examples of Newtonian liquids are water, light oils and other systems in which the dissolved subtance has a low mole mass, does not associate with other dissolved particles and only exhibits limited interaction with the solvent (dispersion medium). 

At constant temperature and pressure, V is proportional to n and thus to mass. In this way, the ideal gas law provides us with a connection to the mole/mass relations implied by a chemical equation. 

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