Solution mole-mass-number-volume

Any solution contains at least two chemical species, the solvent and one or more solutes. The mass of a solution is the sum of the masses of the solvent and all dissolved solutes. To answer questions such as How much is there about solutions, we need to know the amount of each solute present in a specified volume of solution. The amount of a solute in a solution is given by the concentration, which is the ratio of the amount of solute to the amount of solution. In chemistry the most common measure of concentration is molarity (M). Molarity is the number of moles of solute (n) divided by the total volume of the solution (V) in liters ... 

The molaLity m is the number of moles of solute dissolved per unit mass of solvent molaRity (note the different spelling) is the number of moles of solute dissolved per unit volume. 

In preparing a molar solution, the correct number of moles of solute (commonly converted to grams using the molar mass) is dissolved and diluted to the required volume. 

The key to any reaction experiment is moles. The numbers of moles may be calculated from various measurements. A sample may be weighed on a balance to give the mass, and the moles calculated with the formula weight. Or the mass of a substance may be determined using a volume measurement combined with the density. The volume of a solution may be measured with a pipet, or calculated from the final and initial readings from a buret. This volume, along with the molarity, can be used to calculate the moles present. The volume, temperature, and pressure of a gas can be measured and used to calculate the moles of a gas. You must be extremely careful on the AP exam to distinguish between those values that you measure and those that you calculate. 

A—To calculate the molality of a solution, both the moles of solute and the kilograms of solvent are needed. A liter of solution would contain a known number of moles of solute. To convert this liter to mass, a mass to volume relationship (density) is needed. 

The desired quantity is the volume of solution. The available data are the molarity of HCl in solution, the mass of chalk, and the molar mass of CaCOo. In addition, two relations are required. One identifies cnalk as calcium carbonate by stating that the mass of chalk equals the mass of CaC0 . Another gives the stoichiometry by saying that two times the number of moles of CaCO equals the number of moles of HCl. The diagram showing the solution in this case occupies several screens a separate screen is used to show each application of a relation. 

A I he numbers of moles of the compounds in 100 g of water are obtained by dividing the mass of the compounds by their relative formula masses. The volumes of the solutions in dm arc obtained hy dividing the total mass bv the density. Dividing the numbers of moles of the halides by the volumes of their solutions gives the required molar concemralions. The answers are ... 

CONCENTRATION (Chemical). The quanlily of matter or of a particular type of matter that exists in a unit volume, as the strength of a solution in mass of solute per unit mass of solution or in the number of moles, hydrogen ions, etc., contained per unit volume or per unit mass. 

Then use this molarity as a conversion factor to calculate the number of moles of solute in the stated volume of solution. The mass of solute is given and the number of moles of solute present is now known therefore, to find the molar mass of the solute, divide the mass by the amount. To avoid rounding errors, do the numerical calculation at the end. 

The advantages of using molarity are twofold (1) Stoichiometry calculations are simplified because numbers of moles are used rather than mass, and (2) amounts of solution (and therefore of solute) are measured by volume rather than by mass. As a result, titrations are particularly easy (Section 3.10). 

To prepare a 1.000 m solution of KBr in water, for example, you would dissolve 1.000 mol of KBr (119.0 g) in 1.000 kg (1000 mL) of water. You can t say for sure what the final volume of the solution will be, although it will probably be a bit larger than 1000 mL. Although the names sound similar, note the differences between molarity and molality. Molarity is the number of moles of solute per volume (liter) of solution, whereas molality is the number of moles of solute per mass (kilogram) of solvent. 

In the case of solutions (liquid or solid mixtures), besides the molar fraction, we frequently use for expressing the solution composition the molar concentration (or molarity) ct, the number of moles for unit volume of the solution, and the molality mt, the number of moles for unit mass of the solvent (main component substance of the solution) ... 

To perform a degree-of-freedom analysis on a single-unit nonreactive process, count unknown variables on the flowchart, then subtract independent relations among them. The difference, which equals the number of degrees of freedom for the process, must equal zero for a unique solution of the problem to be determinable. Relations include material balances (as many as there are independent species in the feed and product streams), process specifications, density relations between labeled masses and volumes, and physical constraints (e.g., the sum of the component mass or mole fractions of a stream must add up to 1.)... 

For any case in which F is zero, a definite reproducible solubility equilibrium can be reached. Complete representation of the solubility relations is accomplished in the phase diagram, which gives the number, composition, and relative amounts of each phase present at any temperature in a sample containing the components in any specified proportion. Solubilities may therefore be expressed in any appropriate units of concentration, such as the quality of the solute dissolved (defined mass, number of moles) divided by the quantity either of the solvent (defined mass, volume, or number of moles) or of the solution (defined mass, volume, or number of moles). Jacques et al. (1981) have provided a compilation of the expressions for concentration and solubility. 

To calculate molarity, the amount of NaOH must be in moles, and the volume of solution must be in liters. 850 mL is 0.850 L. Knowing that 1.00 mole of NaOH has a mass of 40.0 g, the number of moles of NaOH in the solution is... 

The advantage of molarity is that it is generally easier to measure the volume of a solution, using precisely calibrated volumetric flasks, than to weigh the solvent, as we saw in Section 4.5. For this reason, molarity is often preferred over molality. On the other hand, molality is independent of temperature, since the concentration is expressed in number of moles of solute and mass of solvent. The volume of a solution typically increases with increasing temperature, so that a solution that is 1.0 M at 25°C may become 0.97 M at 45°C because of the increase in volume. This concentration dependence on temperature can significantly affect the accuracy of an experiment. Therefore it is sometimes preferable to use molality instead of molarity. 

In dilute solution, the total number of moles of solute and solvent in unit volume will approach Ci, the molar concentration of solvent. Then the mole fraction X2 of solute can be expressed as X2 = C2/(Ci+C2) - C2/Ci, where C2 is the molar concentration of solute. If the mass/volume concentration of solute is C2 and M2 is the molecular weight of... 

Many environmental reactions and almost all biochemical reactions occur in solution, so an understanding of reactions in solution is extremely important in chemistry and related sciences. We ll discuss solution chemistry at many places in the text, but here we focus on solution stoichiometry. Only one aspect of the stoichiometry of dissolved substances is different from what we ve seen so far. We know the amounts of pure substances by converting their masses directly into moles. For dissolved substances, we must know the concentration—the number of moles present in a certain volume of solution—to find the volume that contains a given number of moles. Of the various ways to express concentration, the most important is molarity, so we discuss it here (and wait until Chapter 13 to discuss the other ways). Then, we see how to prepare a solution of a specific molarity and how to use solutions in stoichiometric calculations. 

Figure 3.10 Summary of mass-mole-number-volume relationships in solution. The amount (in moles) of a compound in solution is related to the volume of solution in liters through the molarity (M) in moles per liter. The other relationships shown are identical to those in Figure 3.4, except that here they refer to the quantities in solution. As in previous cases, to find the quantity of substance expressed in one form or another, convert the given information to moles first.

In Chapters 3 and 4, we encountered many reactions that involved gases as reactants (e.g., combustion with O2) or as products (e.g., a metal displacing H2 from acid). From the balanced equation, we used stoichiometrically equivalent molar ratios to calculate the amounts (moles) of reactants and products and converted these quantities into masses, numbers of molecules, or solution volumes (see Figure 3.10). Figure 5.11 shows how you can expand your problem-solving repertoire by using the ideal gas law to convert between gas variables (F, T, and V) and amounts (moles) of gaseous reactants and products. In effect, you combine a gas law problem with a stoichiometry problem it is more realistic to measure the volume, pressure, and temperature of a gas than its mass. 

Strictly speaking, the concentration measures per volume of solvent (Bunsen), per number of moles in the solution (mole fraction), and per mass of solution (samples) are not linearly related, and hence Henry s law cannot simultaneously be valid for all forms. To illustrate the problem, consider the conversion from mole fraction concentrations Xi to per weight concentrations Ci ... 

We have the mass (in grams) of solute, so we need to convert the mass of solute to moles (using the molar mass of NaOH). Then we can divide the number of moles by the volume in liters. 

Thinking it Through Often chemical arithmetic is based not on a mass measurement, but on a volume measurement. The molarity of a solution expresses the number of moles of solute in a liter of solution. It is straightforward in this case to predict the volume of SO iaq) that will be required. The SO (aq) is halfes concentrated as the Ff (aq> solution, but only half Has number of moles are required according to the balanced equation. Therefore, 24.0 mL of the SO (aq) will be required for the titration to be completed. This is choice (B). 

Describing the composition of a solution means specifying the amount of solute present in a given quantity of the solution. We typically give the amount of solute in terms of mass (number of grams) or in terms of moles. The quantity of solution is defined in terms of mass or volume. 

When a solution is desaibed in terms of mass percent, the amount of solution is given in terms of its mass. However, it is often more convenient to measure the volume of a solution than to measure its mass. Because of this, chemists often describe a solution in terms of concentration. We define the concentration of a solution as the amount of solute in a given volume of solution. The most commonly used expression of concentration is molarity (Af). Molarity describes the amount of solute in moles and the volume of the solution in liters. Molarity is the number of moles of solute per volume of solution in liters. That is... 

Plan The molarity of a solution is the number of moles of solute divided by the number of liters of solution (Equation 13.8). The number of moles of solute (CyHg) is calculated from the number of grams of solute and its molar mass. The volume of the solution is obtained from the mass of the solution (mass of solute + mass of solvent = 5.0 g + 225 g = 230 g) and its density. 

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