Molarity The number of moles

Molarity, the number of moles of solute per liter of solution, can be used as a factor to find the volume of a solution from the number of moles of solute or vice versa. 

Osmotic pressure is another property due to dissolved substances. The presence of solute particles lowers the ability of solvent molecules to pass through a semipermeable membrane. Osmotic pressure is very important in biological systems, and an application of the theory behind osmotic pressure allows for the purification of seawater. The osmotic pressure of a solution, IT, is proportional to the molarity (the number of moles per liter) ... 

Molarity. The number of moles of solute in one liter of solution. (4.5)... 

From the measured volume of the NaOH solution required for titration and its molarity, the number of moles of NaOH, the moles of acid, and the concentration of the acid are calculated. 

Concentration. The basis unit of concentration in chemistry is the mole which is the amount of substance that contains as many entities, eg, atoms, molecules, ions, electrons, protons, etc, as there are atoms in 12 g of ie, Avogadro s number = 6.0221367 x 10. Solution concentrations are expressed on either a weight or volume basis. MolaUty is the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. Molarity is the concentration of a solution in terms of the number of moles of solute per Hter of solution. 

It is important to realize that a rate and a rate constant are different quantities. However, for a simple rate equation, this interpretation can be given to the rate constant k is the number of moles per liter reacting per unit time when all concentrations are one molar. This interpretation is the basis of the synonym specific rate for the rate constant. 

Reality Check Because every known substance has a molar mass greater than 1 g/mol, the mass of the sample in grams is always larger than the number of moles. 

Strategy (1) Start by calculating the number of moles of Fe2+. Then (2) use the coefficients of the balanced equation to find the number of moles of Mn04. Finally, (3), use molarity as a conversion factor to find the volume of KMn04 solution. 

Most commonly, the amount of matter in a gaseous sample is expressed in terms of the number of moles (n). In some cases, the mass m in grams is given instead. These two quantities are related through the molar mass, MM ... 

In taking these sums, the standard molar entropies are multiplied by the number of moles specified in the balanced chemical equation. 

Molal boiling point constant, 269,270t Molal freezing point constant, 269,270t Molality (m) A concentration unit defined as the number of moles of solute per kilogram of solvent, 259,261-262 Molar mass The mass of one mole of a substance, 55,68-68q alcohol, 591 alkane, 591... 

Chemists often indicate the concentration of a substance in water solution in terms of the number of moles of the substance dissolved per liter of solution. This is called the molar concentration. A one-molar solution (1 M) contains one mole of the solute per liter of total solution. a two-molar solution (2 M) contains two moles of solute per liter, and a 0.1-molar solution (0.1 M) contains one-tenth mole of solute per liter. Notice that the concentration of water is not specified, though we must add definite amounts of water to make the solutions. 

For expressing concentrations of reagents, the molar system is universally applicable, i.e. the number of moles of solute present in 1 L of solution. Concentrations may also be expressed in terms of normality if no ambiguity is likely to arise (see Appendix 17). 

As a result standard solutions are now commonly expressed in terms of molar concentrations or molarity (AT). Such standard solutions are specified in terms of the number of moles of solute dissolved in 1 litre of solution for any solution,... 

For pure substances, n is usually held constant. We will usually be working with molar quantities so that n = 1. The number of moles n will become a variable when we work with solutions. Then, the number of moles will be used to express the effect of concentration (usually mole fraction, molality, or molarity) on the other thermodynamic properties. 

By either a direct integration in which Z is held constant, or by using Euler s theorem, we have accomplished the integration of equation (5.16), and are now prepared to understand the physical significance of the partial molar property. For a one-component system, Z = nZ, , where Zm is the molar property. Thus, Zm is the contribution to Z for a mole of substance, and the total Z is the molar Zm multiplied by the number of moles. For a two-component system, equation (5.17) gives... 

It follows that n — m M. That is, to find the number of moles, n, we divide the total mass, m, of the sample by the molar mass. 

STRATEGY Divide each mass percentage by the molar mass of the corresponding element to obtain the number of moles of that element found in exactly 100 g of the compound. Divide the number of moles of each element by the smallest number of moles. If fractional numbers result, then multiply by the factor that gives the smallest whole numbers of moles. 

The molar enthalpy of combustion increases with molar mass as might be expected, because the number of moles of CO, and H,0 formed will increase as the number of carbon and hydrogen atoms in the compounds increases. The heat released per gram of these hydrocarbons is essentially the same because the H to C ratio is similar in the three hydrocarbons. 

If these equations are written in terms of mass and then summed over all components, the sum must equal Equation (1.1) since the net rate of mass formation must be zero. When written in molar units as in Equation (1.6), the sum need not be zero since chemical reactions can cause a net increase or decrease in the number of moles. 

Batch reactors give the lowest possible fraction unreacted and the highest possible conversion for most reactions. Batch reactors also give the best yields and selectivities. These terms refer to the desired product. The molar yield is the number of moles of a specified product that are made per mole... 

To integrate this, u is needed. When there is no change in the number of moles upon reaction. Equation (3.2) applies to the total molar density as well as to the mass density. Thus, for constant A, ... 

We are now ready to calculate the mean residence time. According to Equation (1.41), f is the ratio of mass inventory to mass throughput. When the number of moles does not change, t is also the ratio of molar inventory to molar throughput. Denote the molar inventory (i.e., the total number of moles in the tube) as Nactimi- Then... 

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