high melting point, hard, brittle, slightly soluble in water, conductor of electricity when melted or in solution Molecular solid - crystalline solid that has molecules arranged in a particular configuration. low melting point, generally insoluble in water, nonconductor of electricity. Metallic solid - crystalline solid that has atoms of metals arranged in a definite pattern. low to high melting point, malleable, ductile, conductor of electricity, insoluble in most solvents. Lesson 13.6 Changes of physical state: * necessary to draw a temperature-energy graph to see the change in temperature with a constant application of heat Heat of fusion - the amount of heat required to melt 1.00 g of substance.
1) Jeffrey Cox CHE111-DL01 Lab number 10 Stoichiometry of a Precipitation Reaction 2) Purpose/ Intro. In this lab we will be able to calculate the actual, theoretical, and percent yield of the product from a precipitation reaction. We will thusly learn the concepts of solubility and the formation of a precipitate. A precipitate reaction is a reaction in which soluble ions in separate solutions are mixed together to form an insoluble compound that settles out of the combined solution as a solid. The solid then is the insoluble compound, called a precipitate.
Each of these types of reactions behaves in a similar fashion. They all involve the conversion of one substance to another substance, while preserving the original elements in some form. Another aspect of predicting products is the chart of reactivity. In order for the replacement of an element in a compound to happen, the element replacing the original element must be more reactive. The chart of reactivity tells chemists the comparable reactivity of elements.
This lab will also rely on some skills and techniques that were utilized in previous experiments, such as the using of amphoteric metals, amphoteric hydroxide solutions, and complex ion formation. Amphoterism is the ability of a substance to react with either bases or acids. An example of an amphoteric metal is Beryllium. Beryllium and all other amphoteric metals form insoluble hydroxides in limited hydroxide solutions and soluble, complex ions when they are in the presence of excess hydroxide solutions. Similar to Beryllium, Zinc and Chromium are amphoteric, but Iron and Magnesium are not amphoteric, meaning that they form insoluble precipitates in basic solutions like excess hydroxide.
This technique prevents the product to contact other reactants, and leave the heating environment which might cause side reactions. The removal of the product also helps to shift the equilibrium position of the incomplete reaction to the right hand side, and prevents backwards reaction, resulting in an increased yield of products. This experiment also introduces the idea of azeotrope. An azeotrope is a mixture of two or more pure compounds in such a ratio that its composition cannot be changed by simple distillation. This is because when an azeotrope is boiled, the resulting vapour has the same ratio of constituents as the original mixture of liquids.
Although, Ionic bonding is when an atom gives away elections to another atom, which only happens in a metal and a nonmetal, and they have high melting points and are soluble. By investigating the unknown
Purpose: The following lab was conducted in order to determine the iron (〖Fe〗^(2+)) content in an unknown sample by way of reduction-oxidation titration using a standardized potassium permanganate solution. Theory: Titration is one of the most commonly used methods for determining the amount or concentration of an unknown substance. Chemical analysis can be performed on redox titrations, if the following conditions are met: “The reaction is thermodynamically spontaneous enough to be stoichiometric”, “The reaction is kinetically fast enough to give operationally ‘instant’ results”, “No side reactions occur”, and “a satisfactory indicator exists”. These conditions are what makes potassium permanganate (〖KMnO〗_4) a very useful analytical oxidation agent as it easily fits the criteria. The half reactions for this system are: Oxidation of 〖Fe〗^(2+): 〖Fe〗^(2+)→ 〖Fe〗^(3+)+1e^- Reduction of 〖MnO〗_4^-: 〖MnO〗_4^-+8H_3 O^++5e^-→ 〖Mn〗^(2+)+12H_2 O Which produces the following overall equation: 〖MnO〗_4^-+8H_3 O^++5〖Fe〗^(2+)→5〖Fe〗^(3+)+〖Mn〗^(2+)+12H_2 O Equilibrium is initially obtained at a very slow rate, therefore the titration is carried out in the presence of excess sulphuric acid (H_2 〖SO〗_4) at a high temperature; in order to drastically increase the rate at which equilibrium is attained.
We expect Pentane to be the most ideal because it’s boiling point is the furthest away from the boiling point of water. To test our hypothesis, we used heat to vaporize each gas, an ice bath to cool the gases down and measured the condensed liquid gas to calculate each gas’s constant. Methods: In this experiment, we first measured the mass of an empty flask using
Explain your answer. The freezing of mercury is a reversible physical change because the change can be reversed by melting the frozen mercury so it is liquid again. Practice Problem #10 on page 46 10. Air is mainly a mixture of nitrogen and oxygen, with small amounts of other gases such as argon and carbon dioxide. What property could you use to separate the gases in the air?
Chapter Two: Freezing Point Depression Measurements Purpose: The purpose of this lab is to measure freezing points and freezing point depression for several solutions. The freezing point depression constant (Kf) for p-xylene was calculated from freezing point measurements and used to estimate the molar masses of three unknown solutes in a p-xylene solution. The end goal of this lab experiment is to correctly identify these three unknown solutes. The molar mass of a solute is able to be determined through freezing point depression measurements because the increase in solutes disrupts crystal formation, requiring a lower temperature to form a lattice. This colligative property is important in many industries, but is clear to see when using ordinary salt to remove ice from steps or a driveway.