Distinguish between an element and a compound with 2 examples for each An element is a substance that cannot be broken down into any simpler substances. Some examples of Elements are Hydrogen and Helium. A Compound is when two or more elements combine. Examples of this are Water (H2O) and Salt (NaCl) Explain the relationship between the group number and the number of electrons in the valence shell The relationship between the group number and the numebr of
of moles of Cu2O = no. of moles of O = 0.00875 mol (critical step) mass of Cu2O = 0.00875 x (63.5 x 2 + 16.0) = 1.25125 g percentage by mass of Cu2O = (1.25125 )/2.02 x 100 % = 61.9 % Common mistake: no. of moles of (Al2O3 + Cu2O) = Comment: no. of moles = Example 2 0.144 g of a binary compound of aluminium and carbon reacts with an excess of water to produce a gas. This gas burns completely in oxygen to form water and 72 cm3 of carbon dioxide only.
B) permanent dipoles of molecules containing covalent bonds between atoms of very different electronegativities. C) the hydrophobic effect. D) ion pairing between oppositely charged functional groups. Answer: A Page Ref: Section 5 28) The aggregation of nonpolar molecules or groups in water is thermodynamically due to the A) increased entropy of the nonpolar molecules when they associate. B) decreased enthalpy of the system.
Multiple resonance is created from the movement of electrons. The hydrogen atom which is released reacts with HSO4 to make sulphuric acid H2SO4 which is known to be used as a catalyst. The mechanism is as follows: [pic] Health and safety: |Chemical Name |Oxidising |Flammable |Toxic |Harmful |Corrosive |Irritant |Carcinogenic | |Sulphuric acid | | | | | | | | |Methyl Benzoate | | | | | | | | |Methanol | | | | | | | | |Nitric Acid | | | | | | | | You will be using very harmful drugs so before starting make sure te
The net reaction is: This reaction has been studied extensively and occurs for a wide variety of ketones. In general, the halogenations of a ketone can be represented as follow: The main evidence for any mechanism is provided by kinetic studies to determine an experimental rate law. Following the rate law of chemical kinetics, the differential rate equation for the reaction could be written as follow: Where k = rate constant; a, b,c are the orders of the reaction of S, I3-, and H+ respectively. I3- ion is the only coloured species in the reaction mixture, a spectrophotometer can is used to measure the change in its concentration, by applying the Beer-Lambert Law Where A= absorbance, ε= molar absorption coefficient, [I3-]= concentration and /= optical path length, that is, the distance travelled by the light through the solution. The ideal wavelength for the measurement of
Let’s call this number X. Then the structural formula of BaCl2 hydrate can be written as BaCl2•XH2O. The reaction of dehydration is |BaCl2•XH2O ( BaCl2 + XH2O |(5) | According to the stoichiometry of the reaction (5) |[pic] |(6) | Where N1 is the number of moles of BaCl2 formed in the reaction (5) and N2 is the number of moles of water lost in the reaction (5). To find out N1 you need to divide the mass of BaCl2 after the reaction by its molar mass. To find out N2 you have to determine the mass of water produced in the reaction.
This solution was placed in a burette and 18.4 cm3 was required to neutralise 25 cm3 of 0.1 moldm-3 NaOH. Deduce the molecular formula of the acid and hence the value of n. 5. Sodium carbonate exists in hydrated form, Na2CO3.xH2O, in the solid state. 3.5 g of a sodium carbonate sample was dissolved in water and the volume made up to 250 cm3. 25.0 cm3 of this solution was titrated against 0.1 moldm-3 HCl and 24.5 cm3 of the acid were required.
All diisocyanate are liquids or solids in the nature and highly reactive, it undergo reaction across the double bond C=N of the –NCO group. The reactivity of the isocyanates are mainly depends on the electron density of the central carbon atom of the isocyanate, the low electron density of central carbon atom contains compounds are highly reactive means the aromatic diisocyanates are highly reactive than aliphatic because of resonance structures. Therefore, the electrophilic nature of the aromatic diisocyanates can alter through different substituents on aromatic ring like electron withdrawing or donating groups. The reactivity of diisocyanates plays important role to synthesis of polyurethanes because the possibility to form dimers, trimmers and higher oligomers and also possible to form polymers. In addition, the number of cross-linking reactions may be take place, mainly depends on the reaction conditions such as temperature, catalysts, the structure of the alcohols, amines and isocyanates.
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.
FAST TRACK" HSC Chemistry" The Acidic Environment" By Meihua Gong S " Acidic Discoveries! FAST TRACK" Le Chatelier’s Principle HSC Chemistry" Titra>on and standard solu>ons Esterifica>on S KEY QUESTION : How did knowledge of the composi>on and proper>es of acids has led to changes in the defini>on of acids? Modified from Q 21(5 marks) from 2005 HSC S Antoine Lavoisier S Based on the observa>ons that many non-‐metal oxides (e.g. SO2, CO2) dissolve in water to form acidic solu>ons, in 1779, Lavoisier proposed that the presence of oxygen in chemical compounds were the cause of acidity of substances. S LIMITATION: This theory failed to explain why oxygen-‐containing compounds such as MgO formed basic solu>ons in water and why acids such as HCl was acidic even though it did not contain elemental oxygen in its composi>on.