SASS Chem Rxn Gp I VII Summary

Page 1 ST ANDREW’S SECONDARY SCHOOL NAME CLASS CHEMISTRY The Periodic Table Summary of Chemical Reactions Alkali metals (Group I elements) Reaction with Air/ Oxygen gas Observations Equations Lithium burns with a red flame producing a white solid. Sodium burns rapidly with a bright, yellow flame producing a white solid. Potassium burns vigorously with a bright, lilac flame producing a white solid. • The white solid is produced as the white smoke observed. • The white solid dissolves in water to produce a colourless solution that turns red litmus paper blue. Lithium + Oxygen ® Lithium oxide 4 Li + O2 ® 2 Li2O Sodium + Oxygen ® Sodium oxide 4 Na + O2 ® 2 Na2O Potassium + Oxygen ® Potassium oxide 4 K + O2 ® 2 K2O 11 © UCLES 2012 0652/62/O/N/12 [Turn over For Examiner's Use experiment 2 T h e t e a c h e r w e i g h s o u t 1 0 g of ammonium nitrate crystals. She dissolves them in 100 cm3 of water which has the same temperature as in experiment 1. (ii) The thermometer scale in Fig. 4.2 shows the new temperature. Record it in Table 4.1. [1] 20 10 0 °C temperature of ammonium nitrate solution experiment 2 Fig. 4.2 (iii) Each time, use one word to state the type of reaction that occurs in experiment 1 and experiment 2. experiment 1 experiment 2 [2] experiment 3 The teacher places a piece of sodium in a steel spoon. She heats the spoon until the sodium ignites. Then she lowers the spoon into a gas-jar of oxygen. A f l a m e i s s e e n , t h e g a s - j a r f i l l s w i t h w h i t e s m o k e a n d a w h i t e s o l i d f o r m s o n t h e g a s - j a r wall. This is shown in Fig. 4.3. white solid on gas-jar wall burning sodiumoxygen gas white smoke Fig. 4.3

Page 2 Reaction with Water Observations Equations Lithium moves slowly and randomly on the water surface with a soft ‘hissing’ sound. Sodium melts into smaller pieces that moves rapidly and randomly on the water surface with a ‘hissing’ sound. Potassium burns with a lilac flame that moves very rapidly and randomly on the water surface with a ‘hissing’ sound before exploding. • A colourless solution is obtained that turns red litmus paper blue. • ‘Hissing’ sound is the hydrogen gas evolved as effervescence. Lithium + Water ® Lithium hydroxide + Hydrogen 2 Li + 2 H2O ® 2 LiOH + H2 Sodium + Water ® Sodium hydroxide + Hydrogen 2 Na + 2 H2O ® 2 NaOH + H2 Potassium + Water ® Potassium hydroxide + Hydrogen 2 K + 2 H2O ® 2 KOH + H2 Reaction with Chlorine gas Observations Equations Lithium burns slowly with a red flame producing a white solid. Sodium burns rapidly with a bright, yellow flame producing a white solid. Potassium burns vigorously with a bright, lilac flame producing a white solid. • The white solid is produced as the white smoke observed. • The white s