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 solid dissolves in water to produce a colourless solution that has no effect on red and blue litmus papers. Lithium + Chlorine ® Lithium chloride 2 Li + Cl2 ® 2 LiCl Sodium + Chlorine ® Sodium chloride 2 Na + Cl2 ® 2 NaCl Potassium + Chlorine ® Potassium chloride 2 K + Cl2 ® 2 KCl 6 © UCLES 2007 0654/01/M/J/07 16 A s m a l l p i e c e o f e l e m e n t X is dropped into a bowl of water. The diagrams show what happens. X flame When the reaction stops, the remaining solution turns Universal Indicator blue. To which group of the Periodic Table does element X belong? A 1 B 3 C 5 D 6 17 T h e d i a g r a m s h o w s s o m e o f t h e u s e f u l p r o d u c t s m a n u f a c t u r e d i n t h e c h e m i c a l i n d u s t r y f r o m substance X. plastics fuels lubricants waxes substance X What is substance X? A l i m e s t o n e B m e t h a n e C p e t r o l e u m D salt lithium basin of water 2 0654/21/O/N/14© UCLES 2014 1 Fig. 1.1 shows what happens when a small piece of potassium metal reacts with chlorine gas inside a container. clouds of particles made of a white solid container initially full of chlorine gas flamespotassium Fig. 1.1 When the reaction has finished, particles of a white solid compound are left in the container. (a) (i) Suggest the name of the white solid compound. .......................................................................................................................................[1] (ii) Fig. 1.2 shows diagrams of a potassium atom and a chlorine atom. potassium atom chlorine atom Fig. 1.2 Describe what happens to these atoms when they change into ions. ........................................................................................................................................... ........................................................................................................................................... .......................................................................................................................................[2] pale yellow-green chlorine gaswhite smoke

Page 3 halogens (Group viI elements) Reaction with Water Observations Equations Pale yellow-green gas dissolves rapidly to produce a colourless solution. • Turns blue litmus paper red (due to H+) and then bleaches it (due to ClO–). Red-brown liquid dissolves slowly to produce a pale-yellow solution. • Turns blue litmus paper red (due to H+) and then bleaches it (due to BrO–). Only a very small amount of the purple-black crystals added dissolves very slowly in water to produce a pale-yellow solution. • No effect on blue litmus paper. This reaction is an example of disproportionation reaction, where a single substance is both oxidised and reduced simultaneously. Chlorine + Water ® Hydrochloric acid + Hypochlorous acid Cl2 + H2O ® HCl + HClO Bromine + Water ® Hydrobromic acid + Hypobromus acid Br2 + H2O ® HBr + HBrO Iodine + Water ® Hydroiodic acid + Hypoiodus acid I2 + H2O ® HI + HIO 3 0653/06/O/N/04 [Turn over 1A student did an experiment to find out how temperature affects the activity of the enzyme catalase. Catalase is released from potato cells when they are cut open. The enzyme speeds up the production of oxygen from hydrogen peroxide. •She set up the apparatus as shown in Fig. 1.1. Fig. 1.1 •She put 10 cm3hydrogen peroxide into tube A and measured its temperature. (a)Read the thermometer, Fig. 1.2 below, and write the correct temperature in the table, Fig. 1.3, on page 4. Fig. 1.2 •She cut several identical pieces of potato. •She put one piece of potato into the hydrogen peroxide, placed the bung firmly in the top of tube A and started timing. The oxygen appeared as bubbles in tube B. •She counted the number of bubbles produced during a period of 2 minutes. •She rinsed out tube A, then put 10 cm3fresh hydrogen peroxide into it. •She warmed the tube in a water bath until the temperature of the hydrogen peroxide reached 35 °C. •After replacing tube A in the clamp she added the next piece of potato, started timing and counted the bubbles as before. •She did three further readings at 45 °C, 55 °C and 60 °C. 0 10 20 30°C test-tube B test-tube A water delivery tube clamp stand For Examiner’s Use ©UCLES 2004 Cl2 water test-tube delivery tube Cl2 2  UCLES 2004 0620/06/M/J/04 For Examiner’s Use1An experiment was carried out to find the pH of samples of soil from a farmer’s field. soil sample water filtrate universal indicator C A B ( a ) Identify the pieces of apparatus labelled A, B, C. [3] ( b ) Why was the soil crushed? [2] Br2 dropper I2 4  UCLES 2004 0620/06/M/J/04 For Examiner’s Use3Lead bromide was placed in a tube and connected to an electrical circuit as shown below. bulb dc power supply heat LEAD BROMIDE TOXIC T h e l e a d b r o m i d e