In the consumer and industrial world, the most common method of expressing the concentration is based on the quantity of solute in a fixed quantity of solution. Percent solutions define the quantity of a solute that is dissolved in a quantity of solution multiplied by When making a percent solution, it is important to indicate what units are being used, so that others can also make the solution properly.
Also, recall that the solution is the sum of both the solvent and the solute when you are performing percent calculations. Thus, the following equation can be used when calculating percent solutions:. As an example, a 7. How much water is in the solution? Thus, we can fill in the values and then solve for the unknown. How many grams of NaCl are required to make mL of a For more dilute solutions, parts per million 10 6 ppm and parts per billion 10 9 ; ppb are used.
These terms are widely employed to express the amounts of trace pollutants in the environment. There are also ppm and ppb units defined with respect to numbers of atoms and molecules. The mass-based definitions of ppm and ppb are given here:.
Both ppm and ppb are convenient units for reporting the concentrations of pollutants and other trace contaminants in water. Concentrations of these contaminants are typically very low in treated and natural waters, and their levels cannot exceed relatively low concentration thresholds without causing adverse effects on health and wildlife.
For example, the EPA has identified the maximum safe level of fluoride ion in tap water to be 4 ppm. Inline water filters are designed to reduce the concentration of fluoride and several other trace-level contaminants in tap water Figure 8.
This can be very useful as it is easier for us to think about water in terms of its volume, rather than by its mass. In addition, the density of water is 1. For example, if we find that there is lead contamination in water of 4 ppm, this would mean that there are:.
Concentrations of ionic solutes are occasionally expressed in units called equivalents Eq. One equivalent equals 1 mol of positive or negative charge. In a more formal definition, the equivalent is the amount of a substance needed to do one of the following:. By this definition, an equivalent is the number of moles of an ion in a solution, multiplied by the valence of that ion. The valence of calcium is 2, so for that ion you have 1 mole and 2 equivalents. A solution of a desired concentration can also be prepared by diluting a small volume of a more concentrated solution with additional solvent.
A stock solution , which is a prepared solution of known concentration, is often used for this purpose. Diluting a stock solution is preferred when making solutions of very weak concentrations, because the alternative method, weighing out tiny amounts of solute, can be difficult to carry out with a high degree of accuracy.
Dilution is also used to prepare solutions from substances that are sold as concentrated aqueous solutions, such as strong acids. The procedure for preparing a solution of known concentration from a stock solution is shown in Figure 8. It requires calculating the amount of solute desired in the final volume of the more dilute solution and then calculating the volume of the stock solution that contains this amount of solute. Remember that diluting a given quantity of stock solution with solvent does not change the amount of solute present, only the volume of the solution is changing.
The relationship between the volume and concentration of the stock solution and the volume and concentration of the desired diluted solution can therefore be expressed mathematically as:. Where M s is the concentration of the stock solution, V s is the volume of the stock solution, M d is the concentration of the diluted solution, and V d is the volume of the diluted solution. What volume of a 3. Given: volume and molarity of dilute solution, and molarity of stock solution.
Asked for: volume of stock solution. Strategy and Solution:. For Dilution problems, as long as you know 3 of the variables, you can solve for the 4th variable. Next, check to make sure that like terms have the same units. For example, Md and Ms are both concentrations, thus, to be able to perform the calculations, they should be in the same unit in this case they are both listed in Molarity.
If the concentrations were different, say one was given in Molarity and the other in percent or one was in Molarity and the other was in Millimolarity, one of the terms would need to be converted so that they match.
That way, the units will cancel out and leave you with units of volume, in this case. Finally, fill in the equation with known values and calculate the final answer.
Note that if mL of stock solution is needed, that you can also calculate the amount of solvent needed to make the final dilution. Thus far, we have been discussing the concentration of the overall solution in terms of total solute divided by the volume of the solution. When ionic compounds dissolve in a solution, they break apart into their ionic state.
Cations and anions associate with the polar water molecules. Recall that solutions that contain ions are called electrolyotes , due to their ability to conduct electricity. This can also be thought of on a larger molar scale. To discuss the relationship between the concentration of a solution and the resulting number of ions, the term equivalents is used. It is calculated by dividing the molarity of the solution by the total charge created in the solution.
Water molecules are omitted from a molecular view of the solution for clarity. When we carry out a chemical reaction using a solution of a salt such as ammonium dichromate, we need to know the concentration of each ion present in the solution. If a solution contains 1. The equivalent value of NH 4 2 Cr 2 O 7 can then be calculated by dividing 1. Thus, for NH 4 2 Cr 2 O 7 , dissolving 0.
What are the concentrations of all ionic species derived from the solutes in these aqueous solutions? Given: molarity. Asked for: concentrations. A Classify each compound as either a strong electrolyte or a nonelectrolyte. B If the compound is a nonelectrolyte, its concentration is the same as the molarity of the solution. If the compound is a strong electrolyte, determine the number of each ion contained in one formula unit.
Find the concentration of each species by multiplying the number of each ion by the molarity of the solution. A Sodium hydroxide is an ionic compound that is a strong electrolyte and a strong base in aqueous solution:. Recall from Section 4.
Thus alcohols are nonelectrolytes. One of the great wonders of the cell membrane is its ability to regulate the concentration of substances inside the cell. The phospholipids are tightly packed together, and the membrane has a hydrophobic interior. This structure causes the membrane to be selectively permeable. A membrane that has selective permeability allows only substances meeting certain criteria to pass through it unaided.
In the case of the cell membrane, only relatively small, nonpolar materials can move through the lipid bilayer remember, the lipid tails of the membrane are nonpolar. Some examples of these are other lipids, oxygen and carbon dioxide gases, and alcohol. However, water-soluble materials—like glucose, amino acids, and electrolytes—need some assistance to cross the membrane because they are repelled by the hydrophobic tails of the phospholipid bilayer.
All substances that move through the membrane do so by one of two general methods, which are categorized based on whether or not energy is required. Passive transport is the movement of substances across the membrane without the expenditure of cellular energy.
In contrast, active transport is the movement of substances across the membrane using energy from adenosine triphosphate ATP. You have seen examples of these types of transport mechanisms in Chapter 4, where we learned about the generation of an action potential within a neuron.
In order to understand how substances move passively across a cell membrane, it is necessary to understand concentration gradients and diffusion. A concentration gradient is the difference in concentration of a substance across a space. When molecules move in this way, they are said to move down their concentration gradient.
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. A couple of common examples will help to illustrate this concept. Imagine being inside a closed bathroom. If a bottle of perfume were sprayed, the scent molecules would naturally diffuse from the spot where they left the bottle to all corners of the bathroom, and this diffusion would go on until no more concentration gradient remains. Another example is a spoonful of sugar placed in a cup of tea.
Eventually the sugar will diffuse throughout the tea until no concentration gradient remains. In both cases, if the room is warmer or the tea hotter, diffusion occurs even faster as the molecules are bumping into each other and spreading out faster than at cooler temperatures.
Having an internal body temperature around Whenever a substance exists in greater concentration on one side of a semipermeable membrane, such as the cell membranes, any substance that can move down its concentration gradient across the membrane will do so. Consider substances that can easily diffuse through the lipid bilayer of the cell membrane, such as the gases oxygen O 2 and CO 2.
O 2 generally diffuses into cells because it is more concentrated outside of them, and CO 2 typically diffuses out of cells because it is more concentrated inside of them.
Neither of these examples requires any energy on the part of the cell, and therefore they use passive transport to move across the membrane. Before moving on, you need to review the gases that can diffuse across a cell membrane. Because cells rapidly use up oxygen during metabolism, there is typically a lower concentration of O 2 inside the cell than outside.
As a result, oxygen will diffuse from the interstitial fluid directly through the lipid bilayer of the membrane and into the cytoplasm within the cell. On the other hand, because cells produce CO 2 as a byproduct of metabolism, CO 2 concentrations rise within the cytoplasm; therefore, CO 2 will move from the cell through the lipid bilayer and into the interstitial fluid, where its concentration is lower.
This mechanism of molecules moving across a cell membrane from the side where they are more concentrated to the side where they are less concentrated is a form of passive transport called simple diffusion Figure 8.
Simple Diffusion across the Cell Plasma Membrane. The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion. Large polar or ionic molecules, which are hydrophilic, cannot easily cross the phospholipid bilayer. Very small polar molecules, such as water, can cross via simple diffusion due to their small size. Charged atoms or molecules of any size cannot cross the cell membrane via simple diffusion as the charges are repelled by the hydrophobic tails in the interior of the phospholipid bilayer.
Solutes dissolved in water on either side of the cell membrane will tend to diffuse down their concentration gradients, but because most substances cannot pass freely through the lipid bilayer of the cell membrane, their movement is restricted to protein channels and specialized transport mechanisms in the membrane.
A common example of facilitated diffusion is the movement of glucose into the cell, where it is used to make ATP. Although glucose can be more concentrated outside of a cell, it cannot cross the lipid bilayer via simple diffusion because it is both large and polar.
To resolve this, a specialized carrier protein called the glucose transporter will transfer glucose molecules into the cell to facilitate its inward diffusion.
There are many other solutes that must undergo facilitated diffusion to move into a cell, such as amino acids, or to move out of a cell, such as wastes. Because facilitated diffusion is a passive process, it does not require energy expenditure by the cell.
Water also can move freely across the cell membrane of all cells, either through protein channels or by slipping between the lipid tails of the membrane itself.
Osmosis is the diffusion of water through a semipermeable membrane Figure 8. The movement of water molecules is not itself regulated by cells, so it is important that cells are exposed to an environment in which the concentration of solutes outside of the cells in the extracellular fluid is equal to the concentration of solutes inside the cells in the cytoplasm.
T onicity is used to describe the variations of solute in a solution with the solute inside the cell. Three terms— hypotonic, isotonic, and hypertonic —are used to compare the relative solute concentration of a cell to that of the extracellular fluid surrounding the cells. In a hypotonic solution , such as tap water, the extracellular fluid has a lower concentration of solutes than the fluid inside the cell, and water enters the cell.
Note that water is moving down its concentration gradient If this occurs in an animal cell, the cell may burst, or lyse. Because the cell has a lower concentration of solutes, the water will leave the cell.
In effect, the solute is drawing the water out of the cell. This may cause an animal cell to shrivel, or crenate. In an isotonic solution , the extracellular fluid has the same solute concentration as the cell. If the concentration of solutes of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell. Blood cells in hypertonic, isotonic, and hypotonic solutions take on characteristic appearances as shown in Figure 8. Various organ systems, particularly the kidneys, work to maintain this homeostasis.
Some organisms, such as plants, fungi, bacteria, and some protists, have cell walls that surround the plasma membrane and prevent cell lysis. The plasma membrane can only expand to the limit of the cell wall, so the cell will not lyse. In fact, the cytoplasm in plants is always slightly hypertonic compared to the cellular environment, and water will always enter a cell if water is available.
This influx of water produces turgor pressure, which stiffens the cell walls of the plant Figure 8. In nonwoody plants, turgor pressure supports the plant. If the plant cells become hypertonic, as occurs in drought or if a plant is not watered adequately, water will leave the cell. Plants lose turgor pressure in this condition and wilt. Another mechanism besides diffusion to passively transport materials between compartments is filtration.
Unlike diffusion of a substance from where it is more concentrated to less concentrated, filtration uses a hydrostatic pressure gradient that pushes the fluid—and the solutes within it—from a higher pressure area to a lower pressure area. Filtration is an extremely important process in the body. For example, the circulatory system uses filtration to move plasma and substances across the endothelial lining of capillaries and into surrounding tissues, supplying cells with the nutrients.
As a result, individuals may experience brain and heart complications due to long-term stimulant medication abuse. Ecstasy is an illicit stimulant typically sold at parties or clubs. Ecstasy is different than most stimulants because it increases the amount of serotonin in the brain, rather than dopamine. This drug comes in many different forms, including colorful pills and a crystal-like rock. Individuals may orally ingest, snort, or drop ecstasy in their drinks. This drug causes a heightened sense of pleasure, energy, happiness, love, and sexual desire.
Additionally, this drug is known to have some hallucinogenic properties as well. Despite the pleasurable high ecstasy can produce, this drug can have long-term adverse health effects. The risks of long-term ecstasy abuse include:. If you or a loved one is suffering from stimulant abuse or addiction, it may be time to seek professional addiction treatment.
Stimulant abuse can lead to long-term adverse health effects, causing an individual to experience social, mental, and physical grief.
In order to recover from stimulant addiction, individuals must attend professional detox and inpatient addiction treatment. If you would like to begin a new way of life and beat stimulant addiction, contact Carolina Center for Recovery today.
All of the information on this page has been reviewed and verified by a certified addiction professional. She currently practices in the public domain in South Africa. She has an interest in medical writing and has a keen interest in evidence-based medicine. Popular Post Recent Posts. Abused Substances. The immune system is a complex group of glands, organs, and cells that work together… Read More.
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The increased charge will drag the ligands more strongly leading to a greater perturbation. Given the same ligand, the same geometry, the same oxidation state 10 Dq increases from the first transition series to the second and to the third.
Also, the geometry in all the complexes is the same, octahedral. Cyanide is the strongest and water is the weakest. Get Started for Free Download App. More Periodic Table Questions Q1. Which base is found in window cleaner? Which among the following had not been discovered by the time when Mendeleev published his periodic table? In which form the chemical compound RDX is used? How are the following elements arranged in the Periodic Table?
H, He, Li, Be, and B. Monosodium glutamate MSG in food is used as. Which of the following gases in involve in soft drinks? Which of the following statement is correct? The chemical name of washing soda is sodium carbonate. The chemical name of Baking soda is calcium hypochlorite. Which of the following gas is not a noble gas?
Which of the following metals is used with iron to form stainless steel?
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