Ten grams ( 10 g ) of an impure sample of sodium carbonate is added to \( 100 \mathrm{~cm}^{3} \) of a 0,2 mol \( \mathrm{dm}^{3} \) solution of hydrochloric acid. The acid is in excess. The equation for the reaction is: \( \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \) \( 8.3 .1 \quad \) Balance the equation above. \( 8.3 .2 \quad \) Calculate the number of moles of hydrochloric acid. The excess acid neutralises \( 20 \mathrm{~cm}^{3} \) of a solution of 0,1 mol.dm of magnesium hydroxide. \( 2 \mathrm{HCl}(\mathrm{aq})+\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{aq}) \rightarrow \mathrm{MgCl}_{2} \) (aq) \( +\mathrm{H}_{2} \mathrm{O}(t) \)

57. Rappresenta le equazioni delle seguenti reazioni specificando il nome dei prodotti. \( \begin{array}{ll}\text { a) ossidazione dell'esano } & \text { c) dibromurazione dell'esano } \\ \text { b) monoclorurazione del butano } & \text { d) ossidazione del propano }\end{array} \)

The half-life of the radioactive element unobtanium- 47 is 10 seconds. If 80 grams of unobtanium- 47 are initially present, how many grams are present after 10 seconds? 20 seconds? 30 seconds? 40 seconds? 50 seconds?

At what temperatures is an exothermic reaction spontaneous? A. At higher temperatures when the change in entropy is negative B. At no temperatures C. At all temperatures all the time D. At all temperatures when the change in entropy is positive

Which is the correct Lewis structure for acetylene (\(C_ { 2} H_ { 2} \))?

The electronic configuration of one element is \(1s^ 2 2s^ 2 2p^ 6 3s^ 2 3p^ 6 3d^ { 10} 4s^ 1\). What is same group which is recently discovered?