Grains are regions of irregular structure that exist in the overall crystalline structure of the metal. However, during solidification of a molten metal or recovery from a stressor like beating different regions are forced to crystallize at the same time. The atoms in a metallic solid are arranged in close packed crystalline arrangements as shown above. This is because of the Metallic Microstructure. Smelting or physically beating a metal causes the metal to become stronger. There are three main types of packing in the transition metals: Face-Centred Cubic (FCC), Body-Centred Cubic (BCC) and Hexagonal Close Packed (HCP). This gives metals their ability to conduct heat and electricity well. The nuclei (represented as spheres) are arranged into fixed orientations while the electrons are free to flow around them. Metal atoms are arranged around each other into what is called a cubic cell (shown above). This property of metallic structure comes from their atomic structure: If you beat the metal harder, the layers remain in their new orientation: If the stress is released again, they will fall back to their original positions: If a small stress is put onto the metal, the layers of atoms will start to roll over each other. The properties of malleability and ductility comes from the ability of the atoms in the metal to roll over each other into new positions without breaking the metallic bonds that hold them together. But metals are also hard which means once formed into a shape by smelting (liquefying using heat) or beating, the shape is maintained. Metals can therefore be shaped into almost any form needed. For example, copper can be made into thin sheets and wire because it is both malleable and ductile. A ductile material is one that can be pulled out, or drawn, into a long wire. A malleable (mal ee uh bul) material is one that can be hammered or rolled into flat sheets and other shapes. The physical properties of metals include shininess, malleability, ductility, and conductivity. So what is a metal and what makes it so useful for the creation of weapons? Metal Both guns and knives and other bladed instruments are almost always composed of metal. If you add 2.00 mL of 0.100 M HCl to 100 mL of a buffer consisting of 0.100 M HA and 0.The material that composes most weapons is metal. Calculate pH given the actual concentrations of the conjugate acid and conjugate base. The best indicator for a titration is given by a indicator with pK a or endpoint closest to the pH of the equivalence point.ġ. Indicators are actually weak acids themselves that change color when H + is added or taken away from the structure. The equivalence point is where the amount of protons is equal to the amount of hydroxide ions.į. The optimum area for buffering in a pH curve is in the vicinity where pKa equals the pH (or where the ratio of A- to HA equals 1). The progress of an acid-base titration is often monitored by plotting the pH of the solution being analyzed as a function of the amount of titrant added. Titrations are commonly used to determine the amount of acid or base in a solution. Most effective buffer solutions contain large amounts of acid and conjugate base.Į. Buffer capacity of a buffered solution represents the amount of protons or hydroxide ions the buffer can absorb without a significant change in pH. To find the pH easily the Henderson-Hasselbalch equation can be used:ĭ. If you know the ratio of acid to base and both amounts are large the proton concentration can easily be found using the equation: When hydroxide ions are added to a buffer solution they react with the acid and are replaced by the Anions.Ĭ. Buffered solutions are simply solutions of weak acids or bases containing a common ion. A buffered solution is one that resists a change in its pH when either hydroxide ions or protons are added. The shift in equilibrium position that occurs because of the addition of an ion already involved in the equilibrium reaction is called the common ion effect.ī. When a weak acid solution has common ions added by a salt, the equilibrium will shift by Le Chatelier's principle.
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