12.5. Identification of ions and gases
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 359 questions
Calcium carbonate was heated strongly in a test-tube. The gas given off was bubbled through limewater. heat calcium carbonate limewater What type of chemical reaction occurs when calcium carbonate is heated strongly? Put a ring around the correct answer. hydration neutralisation oxidation thermal decomposition State the name of the gas given off when calcium carbonate is heated strongly. State the colour change of the limewater. The product remaining in the test-tube is calcium oxide. Calcium oxide is used in steelmaking. Describe how and why calcium oxide is used in making steel. Steel is an alloy. What do you understand by the term alloy ? Give one other use of calcium oxide. Complete the symbol equation for the reaction of calcium oxide with hydrochloric acid. CaO + HCl → CaCl 2 + State the chemical name of the compound CaCl 2.
0620_w10_qp_21
THEORY
2010
Paper 2, Variant 1
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The table shows the mass of some ions present in a 500 cm3 bottle of mineral water. name of ion symbol mass of ion / mg calcium Ca2+ 40.5 Cl – 8.1 magnesium Mg2+ 11.6 nitrate NO3 – 2.4 potassium K+ 0.9 SO4 2– 6.4 State the name of the following ions. Cl – SO4 2– Calculate the mass of magnesium ions in 100 cm3 of this mineral water. Describe a test for nitrate ions. The gas produced in this test turns damp red litmus paper blue. State the name of this gas. The apparatus shown is used to get pure water from impure mineral water. heat mineral water Complete the diagram by putting the correct labels in the three boxes. Describe how this apparatus separates pure water from dissolved ionic solids. Water purity is important in everyday life. Describe one other area of everyday life where purity of substances is important.
0620_w10_qp_21
THEORY
2010
Paper 2, Variant 1
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A student studied the reaction of citric acid with sodium hydrogen carbonate. She put a solution of citric acid in a plastic cup and measured its temperature. She then added sodium hydrogen carbonate powder and measured the temperature again. thermometer plastic cup sodium hydrogen carbonate citric acid solution lid The temperature of the reaction mixture decreased. Which one of these statements about this reaction is correct? Tick one box. The reaction released heat energy. The reaction is exothermic. The reaction is endothermic. The products have less energy than the reactants. The structure of citric acid is shown below. COOH CH2 C COOH HO CH2 COOH On this structure, put a ring around the alcohol functional group. Write the simplest formula for citric acid. Salts of citric acid can be prepared from lemon juice. The lemon juice is fi rst boiled to remove various substances including enzymes. What do you understand by the term enzyme? The lemon juice is then neutralised with calcium carbonate and solid calcium citrate is formed. Suggest how the calcium citrate can be separated from the mixture. Carbon dioxide gas is released when citric acid solution reacts with calcium carbonate. Describe a test for carbon dioxide. test result The concentration of a citric acid solution can be found by carrying out a titration using the apparatus shown below. sodium hydroxide solution citric acid solution Describe how to carry out this titration.
0620_w11_qp_21
THEORY
2011
Paper 2, Variant 1
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Match the phrases on the left with the defi nitions on the right. The fi rst one has been done for you. relative formula mass an atom that has become charged molecule the smallest part of an element which can take part in a chemical change atom two or more atoms covalently bonded together ion the sum of the relative atomic masses in a compound Sodium hydroxide, NaOH, is an ionic compound which dissolves in water to form a strongly alkaline solution. Which one of the following best describes the pH of a concentrated aqueous solution of sodium hydroxide? Put a ring around the correct answer. pH 2 pH 5 pH 7 pH 8 pH 13 Calculate the relative formula mass of sodium hydroxide. The equation describes how sodium hydroxide reacts with hydrochloric acid. NaOH + HCl → NaCl + H2O What type of chemical reaction is this? A student used a syringe to add 1 cm3 portions of hydrochloric acid to an aqueous solution of sodium hydroxide. hydrochloric acid syringe sodium hydroxide solution Describe how the pH of the solution in the beaker changes as the hydrochloric acid is added until the acid is in excess. The diagram shows the apparatus used to electrolyse concentrated aqueous sodium chloride. anode cathode concentrated aqueous sodium chloride gases + – Give a description of this electrolysis. In your description include ● what substance the electrodes are made from and the reason for using this substance ● what you would observe during the electrolysis ● the names of the substances produced at each electrode.
0620_w11_qp_22
THEORY
2011
Paper 2, Variant 2
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Questions Discovered
359