Solutions calculating moles

Remember that, in general, polyatomic ions remain as intact units in solution. Calculating moles of NH4 ions ... 

Procedure. Calculate the heats of solution of the two species, KF and KF HOAc, at each of the four given molalities from a knowledge of the heat capacity. Calculate the enthalpy of solution per mole of solute at each concentration. Find... 

Generally, these concentrations are expressed in terms of moles of solute per mole of pure solvent (liquid phase) and moles of solute per mole of inert gas (gas phase), thus making the material balance calculations easier. 

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

To determine the activity coefficient, 7r. i, one measures the melting temperature, T, of a solution with mole fraction,. V], and calculates a from equation (6.166). The activity coefficient is then obtained from... 

Step 2 Use this molarity to calculate the amount of solute, Solute (in moles), in the stated volume, V (in liters), of solution ... 

C03-0121. For each of the following salt solutions, calculate the amounts in moles and the numbers of each type of... 

C03-0122. For each of the following salt solutions, calculate the amounts in moles and the numbers of each type of Ion (a) 2.87 L of 0.0550 M lithium carbonate (b) 325 mL of a solution that contains 1.02 X lO formula units of sodium hydrogen sulfate and (c) 2.55 mL of a solution that contains 263 mg/L of sodium oxalate. 

Even in relatively concentrated solutions, the mole fraction of water remains close to 1.00. At a solute concentration of 0.50 M, for example, H2 O = 0.99, only 1% different from 1.00. Equilibrium calculations are seldom accurate to better than 5%, so this small deviation from 1.00 can be neglected. Consequently, we treat solvent water just like a pure substance its concentration is essentially invariant, so it is omitted from the equilibrium constant expression. 

Results of adsorption experiments for butylate, alachlor, and metolachlor in Keeton soil at 10, 19, and 30°C were plotted using the Freundlich equation. A summary of the coefficients obtained from the Freundlich equation for these experiments is presented in TABLE IV. Excellent correlation using the Freundlich equation over the concentration ranges studied (four orders of magnitude) is indicated by the r values of 0.99. The n exponent from the Freundlich equation indicates the extent of linearity of the adsorption isotherm in the concentration range studied. If n = 1 then adsorption is constant at all concentrations studied (the adsorption isotherm is linear) and K is equivalent to the distribution coefficient between the soil and water (Kd), which is the ratio of the soil concentration (mole/kg) to the solution concentration (mole/L). A value of n > 1 indicates that as the solution concentration increases the sorption sites become saturated, resulting in a disproportionate amount of chemical being dissolved. Since n is nearly equal to 1 in these studies, the adsorption isotherms are nearly linear and the values for Kd (shown in TABLE IV) correspond closely to K. These Kd values were used to calculate heats of adsorption (AH). 

Calculate the molality of a solution with mole fraction 0.100 of C2H,OH in water. Ans. Assume 1.00 mol total, which contains ... 

For each solution, calculate the number of moles of acid added. The moles of acid was constant for each solution,... 

For each solution, calculate the number of moles of OH added. 

Next, let s see how we can use molarity to calculate moles. How many moles of ammonium ions are in 0.100 L of a 0.20 M ammonium sulfate solution ... 

Measurements include initial and final masses, and initial and final volumes. Calculations may include the difference between the initial and final values. Using the formula mass and the mass in grams, moles may be calculated. Moles may also be calculated from the volume of a solution and its molarity. 

Concentration problems are concerned with the definitions of the various units. It is possible to calculate the mass and/or volume of the solvent and solute by taking the difference between the final and initial measurements. The density, if not given, is calculated, not measured. It is important to recognize the difference between the values that must be measured and those that can be calculated. Moles are also calculated, not measured. 

A few gases may be involved in some enzyme reactions, e.g., C02 and 02 as used by carbonic anhydrase and produced by catalase, respectively. If the presence of such dissolved gases affects rates and equilibria at ordinary pressure, their importance will increase at higher pressure. Henry s law says that the partial pressure of a gas above a solution is proportional to its mole fraction in the solution. At high pressure it is more correct to speak of the fugacity / of a gas, instead of partial pressure, in the same sense that one uses activity instead of concentration in solution calculations. In dilute solutions, the fugacity of the dissolved gas is given by... 

Fig. 12.14 Cell in which a 30% solution of HC1 in H2O evaporates into a column of air. Mole fractions at the liquid-vapor interface are taken to be their equilibrium values. A stream of dry air flows past the open top of the cylinder, dropping the mole fractions of HC1 and H2O to zero. Calculated mole fractions as a function of height along the tube are shown.

SI base units include the meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), and mole (mol). Derived quantities such as force (newton, N), pressure (pascal. Pa), and energy (joule, J) can be expressed in terms of base units. In calculations, units should be carried along with the numbers. Prefixes such as kilo- and milli- are used to denote multiples of units. Common expressions of concentration are molarity (moles of solute per liter of solution), molality (moles of solute per kilogram of solvent), formal concentration... 

From the given volume and concentration of NaOH solution, calculate the moles of NaOH given (used) ... 

If an ionic substance such as NaCl is the solute, we have to calculate mole fractions based on the total concentration of solute particles (ions) rather than NaCl formula units. A solution of 1.00 mol NaCl in 15.0 mol water at 25°C, for example, contains 2.00 mol of dissolved particles (assuming complete dissociation), resulting in a mole fraction for water of 0.882 and a solution vapor pressure of 21.0 mm Hg. 

Mole fraction is calculated as follows What is the mole fraction of carbon dioxide, (C02), in a mixture of 67.4 g of carbon dioxide in 587 g oxygen (02) 67.4 g x 1 mole/44.0 g = 1.53 mole carbon dioxide. 587 g x 1 mole/32.0 g = 18.4 moles oxygen. Moles of solution = 1.53 moles carbon dioxide + 18.4 moles oxygen = 19.9 moles of solution. The mole fraction of carbon dioxide is 1.53 divided by 19.9 =. 0769. The mole fraction of oxygen must be. 925 since the mole fraction of the solute and the mole fraction of the solvent equal one. 

Calculate the concentration of the saturated solution in grams solute per 100 ml solvent and in moles of solute per liter of solution. In order to calculate moles /liter (M), known as molarity of a solution, it is necessary to change... 

When a solution is diluted, it is useful to know the resulting concentration of the diluted solution in moles per liter, molarity (M). When a solution is diluted, the moles of solute remain constant. Therefore, the volume (V) in liters times the concentration (M) of the original solution (o) equals the volume (V) times the concentration (M) of the final solution (f). In equation form, M0 V0 = Mf Vf. Take 10.0mlofa0.10M copper sulfate solution. Add 2.0 ml of water to the original solution and calculate the molarity of this new solution. Continue to add 2.0 ml of water to each subsequent solution until no color is visible. Calculate the molarity of the final solution. Explain how colored particles can be present in a colorless solution. 

Solution concentration can also be presented as moles of solute in 1 L of solution. This is called the molarity (M) of the solution. Calculate the molarity... 

C. 3, oxide 3, 0.5%, KoX 0.01, C 1. These constants were chosen arbitrarily to approximate roughly the data that we observe in Figure 7. These constants are not unique other sets of constants could also represent the data. The calculations shown are for sorption of a trivalent ion from a solution of a monovalent salt like NaCl. Unless otherwise stated in these Figures, the concentration of the salt is 0.01 M, the capacity of the clay is assumed to be one equivalent per kilogram, p 0 and K (for the clay) is assumed to be 1.0. These numbers give calculated values of D which are similar to those that we observe in our experiments. In our calculations, D is expressed in L/kg, C in equivalents/kg, concentrations in solution as moles/L, and concentrations on the solid (loading) as moles/kg, and units of K or KqX which are consistent with these units. 

The mole fraction (X or x, depending on the author) of any component in a solution is defined as the number of moles (n) of that component, divided by the total number of moles of all components in the solution. The sum of the mole fractions of all components of a solution in mole fractions is 1. In a two-component solution, the mole fraction of a component is calculated by... 

First, we need to calculate the mole fraction of the water. Since the solution is 5.0% (w/w), a-100 g sample of the solution would contain 95 g of water and 5 g of sucrose. To find the mole fraction, we need find the moles of each compound. Recall we calculated mole fractions in chapter 6. 

Lewis and Randall give an example of calculating the activity of a solute from its vapour pressure. When a solution is in equilibrium with the vapour of the solute x2, we may measure the vapour pressure of x2 over a range of concentrations, and by knowing the fugacity of the vapour at each pressure we may obtain the activity of the solute in the solution. When we may assume that the vapour is a perfect gas, the activity a2 in the solution may be taken as proportional to p2, the vapour pressure of the solute. Hence, as we pass from the mole fraction N2 to an infinitely dilute solution of mole fraction Nx2... 

This calculation can be carried out for each quantity of H20 for which data are given. The results are then conveniently represented graphically by a plot of AH, the heat of solution per mole of solute, vs. n, the moles of solvent per mole of solute. The composition variable, n = n2/rti, is related to x ... 

Molar concentration is particularly useful to chemists because it is related to the number of particles in a solution. None of the other measures of concentration are related to the number of particles. If you are given the molar concentration and the volume of a solution, you can calculate the amount of dissolved solute in moles. This allows you to solve problems involving quantities in chemical reactions, such as the ones on the following pages. 

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