8. The radii of Si atoms and V are equal (r = 1,34 A), why is it so different properties?
38. Why is H2O - liquid, a H2S - the gas? Compare their boiling point, melting point.
68. During the combustion of 1 liter of acetylene was allocated 56 kJ of heat Calculate the heat of formation of acetylene C2H2. 298 ΔH °, ΔS ° 298, ΔG ° 298 (see. The task number 67).
98. How many times will increase the rate of chemical reaction A + 2B → C under increasing pressure in the system is 4 times and the simultaneous increase in temperature of 40 ° C? Reactants - gases. The temperature coefficient of the reaction is considered to be 2.
128. Calculate the equilibrium constant of a chemical reaction at 1000K, if the standard Gibbs energy of the reaction at, this temperature is -19,1kDzh / mol. (Answer: Cr = 10)
158. What is more alkaline solution: Na2SO3 or Na2SiO3? Make molecular and ion-molecular reaction equations.
198. The reactions expressed by the following scheme:
KI + KIO3 + H2SO4 → I2 + K2SO4 + H2O
Cd + KMnO4 + H2SO4 → CdSO4 + MnSO4 + K2SO4 + H2O
Make electronic equation. Arrange the coefficients in the reaction equation. For each reaction, specify what substance is an oxidizing agent, a reducing agent: ka-something material is oxidized, some restored. Which group are redox reactions?
208. Chart concentration cell at aZn2 + = 10-2 mol / l at one electrode and aZn2 + = 10-6 mol / l in the other electrode. Indicate which of the electrodes is an anode, a cathode. Calculate the EMF element. (Answer: E ° = 0,118 VA)
Concentration called galvanic cell, wherein the electrodes are made of a metal and immersed in the solution as its salt but different concentrations.
238. In the electrolysis of the copper sulfate solution at the anode allocated 500 ml of oxygen measured at standard conditions How many grams of copper distinguished on the cathode?
268. What is the mechanism of destruction of aircraft electrical cables from corrosion? What type of corrosion.
298. Which of the following molecules are polar polymers: Teflon, butadiene, polyvinyl chloride, polystyrene. Justify your answer.
328. Polivinilftoridnoe coating has high strength, the weak adhesive properties, resistance to humidity and temperature fluctuations. Give an explanation of these properties.
358. How do you explain a great danger of toxic hydrocyanic acid tanks sorting cars? Give a reasoned response.
388. The advantages and disadvantages of using polymeric materials. Specify the possible elimination of some of them. Justify your answer.
418. Calculate the battery life of the iron, if the chemical reaction involved in one kg of iron, the capacitance decreases by 1% per cycle.