You want to control the temperature of an enzyme-controlled reaction that is taking place inside a flask . What is the most effective way to keep the reaction at a controlled and steady temperature? cover the flask with a liel and do not heat tt Bunsen burner flame underneath the flask throughout the reaction water bath Bunsen burner flame underneath the flask every 30 seconds

34 The solubility of KI is 50g in 100g of H_(2)O at 20°C . If 110 grams of KI are added to 200 grams of H_(2)O at the same temperature, A. all of the KI will dissolve. C. the solution will be super saturated. D. asaturated solution will form.

Organic chemistry is an area 1 point of study on matter that does not deal with hydrocarbons and their derivatives. True Flase

AQA GCSE Chemistry for Combined Sciences: Trilogy Oxford University Press Help C2 The periodic table Summary questions 1 a Where in the periodic table do you find: I the halogens + II the noble gases [1 mark] iii the alkali metals [1 mark] [1 mark] b In which groups would you find the three elements described below? I This is a metal that can be cut with a knife and is stored under oil. It reacts violently with water and forms ions with a 1+ charge. [I mark] It This is a very unreactive, monatomic gas. (f mark] iii This toxic gas is the most reactive of the all the non-metallic elements. It forms ions with a 1- charge and will also form covalent compounds. [t mark] 2 Astatine, At, is a halogen whose atomic number is 85. It lies at the bottom of Group 7, beneath lodine a How many electrons occupy its outermost shell (highest energy level)? Explain how you worked out your answer. [I mark] b Predict the state of astatine at 20°C [1 mark] c For the compound sodium astatide, predict: I its type of bonding [1 mark] ii its colour [1 mark] iii its chemical formula [1 mark] iv the word equation and the balanced symbol equation for its formation from its elements [2 marks] v whether or not you would see signs of a reaction if a solution of sodium astatide was mixed with chlorine water. Explain how you arrived at your answer. [2 marks] d Place the halogens, including astatine, in order of reactivity, with the most reactive element first. Explain your answer in detail (include the trend in reactivity and the how the trend can be explained, referring to the formation of halide ions). [6 marks] 3 Rubidium, Rb, is in Group 1 of the periodic table, lying directly beneath potassium. a Predict the following physical properties of rubidium, including its hardness, electrical conductivity, and melting point. [3 marks] b i What will be the charge on a rubidium ion? [1 mark] in Copy and complete the table below: Rubidium compound Chemical formula rubidum iodide rubidum fluoride rubidium lydroside Rubidium compound Chemical formula rubidum iodide rubidum fluoride rubidium lydroside [3 marks] c. Write down word equations and balanced symbol equations, including state symbols, for the following reactions: I rubidium and water [3 marks] it rubidium and chlorine. [2 marks] d Will the reactions of rubidium in part c be more or less vigorous than the same reactions using potassium? Explain your answer in detail by comparing the atoms of the two elements. [5 marks] 4 Group 0 is found as the last column in the periodic table, on the extreme right hand side. a Write the name and symbol of the first four elements in Group 0. [2 marks] b What is the name commonly given to the elements in Group 0? [t mark] c Explain which of the first four noble gases is the odd one out in terms of the number of electrons in its outermost shell. [3 marks] d Describe how the electronic structures of the Group 0 elements affects their chemistry. [1 mark] The Group 0 elements are found in trace amounts in the air. If air is gradually cooled down to extremely low temperatures, predict which of the first four elements would condense as a liquid first. Give a reason for your answer. [2 mark] 5 a Explain how Dmitri Mendeleev used atomic weights to construct his periodic table. [2 marks] b Explain how the scientific community were influenced to accept his periodic table. [6 marks] c Why, in 1869, could scientists not explain why some pairs of elements in his periodic table appeared to be in the wrong order according to their atomic weights? [3 marks] 6 a Explain how the atoms of metals and non-metals change when they react to form their ions, using magnesium as an example of a metallic element and oxygen as an example of a non-metallic element. [6 marks] b Suggest how the radius of a metal ion compares with the radius of the metal atom it was made from. Give a reason for your suggestion. [2 marks] 32

Given that the molar mass of NaCl is 58.44g//mol , what is the molarity of a solution that contains 87.75g of NaCl in 500.mL of solution? Use molarity =(" moles of solute ")/(" liters of solution ") . 0.333M 0.751M 1.50M 3.00M

Which of the following is a set of reducing agents? (A) HNO_(3),Fe^(2+),F_(2) (B) F,Cl^(-).MnO_(4)^(-) (C) I^(-),Na,Fe^(2+) (D) CrO_(7)^(2-)*CrO_(4)^(2-),Na . Which of the following is a redox reaction ? (A) 2CuSO_(4)+4KIlongrightarrowCu_(2)I_(2)+2K_(2)SO_(4)+I_(2) (B) SO_(2)+H_(2)OlongrightarrowH_(2)SO_(3) (C) Na_(2)SO_(4)+BaCl_(2)longrightarrowBaSO_(4)+2NaCl (D) CuSO_(4)+4NH_(3)longrightarrow[Cu(NH_(3))_(4)]SO_(4) (E) C_(12)H_(22)O_(I1)+H_(2)OlongrightarrowC_(6)H_(12)O_(6)+C_(6)H_(12)O_(6) Oxidation number of iodine in IO_(3)^(-),IO_(4)^(-),KI and I_(2) respectively are (A) -1,-1,0,+1 (B) +3,+5,+7,0 (C) +5,+7,-1,0 (D) -1,-5,-1,0 (E) -2,-5,-1,0 .

Question Calcium CARBONATE is the chemical name for... quicklime slaked lime limewater limestone

QUESTION THREE (20 MARKS) a) What do you understand by the term Gibbs free energy? Explain the physical meaning when its value is either negative or positive (3 Marks) b) What is an Ellingham diagram? What is it use in studying properties of materials (4 Marks) c) Discuss the processes involved in the thermal degradation of organic matter at atmospheric pressure (13 Marks) QUESTION FOUR (20 MARKS) a) What are the major highlights of the following types of diffusion i. Steady-state diffusion (5 Marks) ii. Non-steady-state diffusion (5 Marks) b) Explain the various factors that influence diffusion in materials (10 Marks) QUESTION FIVE (20 MARKS) a) Write short notes on: i) Reaction sintering ii) Solid Phase sintering (10 Marks) b) Discus at least ten major harmful effects of corrosion? (10 Marks)

Show Question 89 of 90 68 vv77 True or false? The elements in group 1 of the periodic table do not react with non-metals. FALSE TRUE

Ammonia is made up of hydrogen and nitrogen atoms. The ratio of hydrogen to nitrogen atoms in ammonia is 3:1 . What fraction of the atoms in ammonia are nitrogen atoms?

Sparx Maths 3A= 87 3C 30 3E Summary Booknork codar 32 alvanid A chemical solution contains 7.6ml of water. A chemist adds more water to the solution at a rate of 0.03ml//s . How many seconds will it take for the solution to contain 10ml of water? If your answer is a decimal, give it to 2 d.p. Previous: Watch yidea Antuner