Question Paper 1 |14 Questions| With Correct Answers.

6.1)Complete the dot and cross diagram to show the covalent bonding in a nitrogen molecule, N2 {Ans: Three bonding pairs and two elecrons in each shell}3.4)Suggest why the student warmed the silver iodide, {Ans: To evapourate the water}6.5)A silver nanocrystal is a cube of side 20 nm Calculate the surface area to volume ratio of the nanocrystal. {Ans: Surface area= 6(20x20) =2400 Vol.=20x20x20 =8000 2400:8000= 3:10}3.5)Calculate the percentage atom economy for the production of silver iodide in this reaction. The equation for the reaction is: AGNO3(aq) + Nal(aq) Agl(s) + NaNO3(aq) Relative formula masses (M): AGNO3 = 170 Nal = 150 Agl = 235 NaNO3 = 85 {Ans: Atom enonomy= mr of products/mr of reactants x 100 = 235/(170+150) x100 =73.4%}4.2)Define mass number. {Ans: The number of protons added to the number of neutrons}3.6)Give one reason why reactions with a high atom economy are used in industry. {Ans: They are more profitable}6.2)Explain why nitrogen is a gas at room temperature. {Ans: There are very low intermolecular forces between the moleculeswhich dont take much energy to overcome so its a gas}4.4)Evidence from the alpha particle scattering experiment led to a change in the model