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IGCSE CHEMISTRY
CHAPTER 4
| Question | Answer |
|---|---|
| Two atoms of magnesium, Mg, react with one molecule of oxygen, O². What is the formula of the product? | MgO |
| What are the electrode products when molten silver is electrolysed between inert electrodes? | Cathode - silver Anode - Iodine |
| Ions forms an oxide with the formula Fe²O³. What is the relative formula mass of this compound? | 160 |
| A compound contains one atom of calcium, two atoms of hydrogen and two atoms of oxygen. What is the correct chemical formula of the compound? | Ca(OH)² |
| A compound with the formula XF² has a relative formula mass of 78. What is element X? | Calcium |
| What is the balanced chemical equation for the reaction between calcium and water? | Ca + 2H²O → Ca(OH)² + H² |
| What is the relative molecular mass, M r, of nitrogen dioxide? | 46 |
| Dilute hydrochloric acid reacts with sodium carbonate solution. 2HCl (aq) + Na2CO3(aq) 2NaCl (aq) + H2O(l) + CO2(g). Explain why effervescence is seen during the reaction. | A gas is made |
| What is meant by the term hydrocarbon? | Compound containing carbon and hydrogen only; |
| Give the general formula of straight-chain- Alkanes | nH2n+2 |
| Give the general formula of straight-chain- Alkenes | CnH2n; |
| Name the ester produced from the reaction of propanoic acid and methanol. | Propanoate; |
| What type of polymerisation is used for the production of polyesters? | Condens |
| Which simple molecule is removed when the polyester is formed? | H2O |
| Bromine water changes from brown to colourless when added to X. What does this tell you about the structure of X? | X is alkene |
| Magnesium powder reacts with an aqueous solution of X. Hydrogen is evolved.What does this tell you about the structure of X? | Contains or releases H ions |
| In the conical flas4 there is a neutral solution of potassium sulfate 7hich still contains the indicator used in the titration. Describe how you could obtain a solution of potassium sulfate without the indicator. | Repeat experiment using same volume amount of H2SO4 and same volume amount of KOH |
| Potassium hydrogen sulfate can be made by the following reaction. KOH(aq) + H2SO4(aq) KHSO4(aq) + H2O Suggest how you could make a solution of potassium hydrogen sulfate without using an indicator | Make solution of potassium sulfate by add same volume amount of acid again; Same volume amount of H2SO4 and same volume amount of KOH |
| Describe a test which would distinguish between aqueous solutions of potassium sulfate and sulfuric acid | test: reactive metal / name or formula of suitable metal, e.g. Mg / Fe / Zn; result: bubbles or gas or hydrogen or H2 evolved / dissolves; |
| Copper oxide can be reduced to copper by heating in hydrogen. What colour change would you observe during the reduction? | Black to pink |
| Copper oxide can be reduced to copper by heating in hydrogen. Explain why the copper must be allowed to cool in hydrogen before it is exposed to air. | Hot copper reacts to is oxidised with oxygen or air; |
| Copper oxide can be reduced to copper by heating in hydrogen. Name 3 other gases which can reduce copper(II) oxide to copper | Monoxide Ammonia Methane |
| Copper oxide can be reduced to copper by heating in hydrogen. Name a solid which can reduce copper(II) oxide to copper | Graphite or any metal more reactive than copper |
| Alkenes are unsaturated hydrocarbons. State the general formula of alkenes. | CnH2n |
| Alkenes are unsaturated hydrocarbons. State the empirical formula of alkenes | CH2 |
| What is meant by the term unsaturated? | Multiple bond(s) |
| What is meant by the term hydrocarbon? | Carbon and hydrogen only |
| Describe a test that would distinguish between saturated and unsaturated hydrocarbons. | Bromine water |
| Ethanol is manufactured from glucose, C 6H12O6, by fermentation according to the following equation. C6H12O6 2C2H5OH + 2CO2 State the conditions required for this reaction. | Anaerobic without oxygen 20–40 °C |
| Ethanol can also be manufactured from ethene. Name the raw material which is the source of ethene | Petroleum |
| Ethanol can also be manufactured from ethene. Write a balanced equation for the manufacture of ethanol from ethene. | C2H4 + H2O → C2H5OH |
| Define the the mole? | The number of particles which is equal to the number of atoms |
| Define the Avogadro constant? | The number of particles in one mole of a substance |
| Quantities of chemicals, expressed in moles, can be used to find the formula of a compound, to establish an equation and to determine reacting masses. A compound contains 72% magnesium and 28% nitrogen. What is its empirical formula? | 72/24 = 3 and 28/14 = 2 Mg3N2 |
| A compound contains only aluminium and carbon. 0.03 moles of this compound reacted with excess water to form 0.12 moles of Al(OH)3 and 0.09 moles of CH4. Write a balanced equation for this reaction | Al4C3 + 12H2O = 4Al(OH)3 + 3CH4 |
| 0.07 moles of silicon reacts with 25 g of bromine. Si + 2Br2 SiBr4 Which one is the limiting reagent? Explain your choice | silicon is limiting reagent 0.07 moles of Si and 25/160 = 0.156 moles of Br2 because 0.14 (2 × 0.07) < 0.156 |
| 3.0 g of magnesium was added to 12.0 g of ethanoic acid. Mg + 2CH3COOH → (CH3COO)2Mg + H2 The mass of one mole of Mg is 24 g. The mass of one mole of CH3COOH is 60 g. Which one, magnesium or ethanoic acid, is in excess? You must show your reasoning. | moles of Mg = 3/24 = 0.125 moles of CH3COOH = 12/60 = 0.200 magnesium is in excess |
| 3.0 g of magnesium was added to 12.0 g of ethanoic acid. Mg + 2CH3COOH → (CH3COO)2Mg + H2 The mass of one mole of Mg is 24 g. The mass of one mole of CH3COOH is 60 g. How many moles of hydrogen were formed? | Moles of H2 = 0.1 |
| 3.0 g of magnesium was added to 12.0 g of ethanoic acid. Mg + 2CH3COOH → (CH3COO)2Mg + H2 The mass of one mole of Mg is 24 g. The mass of one mole of CH3COOH is 60 g. Calculate the volume of hydrogen formed, measured at r.t.p. | Volume of hydrogen = 0.1 x 24 = 2.4 dm |
| Soluble salts can be made using a base and an acid. Explain the method of preparing dry crystals of the soluble salt cobalt(II) chloride-6-water from the insoluble base cobalt(II) carbonate. | Step 1 - Add an excess of cobalt(II) carbonate to hot dilute hydrochloric acid. Step 2 - Filter Step 3 - Heat Step 4 - Allow to crystalises |
| Propane reacts with chlorine to form a mixture of chloropropanes. This is a photochemical reaction. What is meant by the phrase photochemical reaction? | A reaction whose rate is influenced by light |
| Chloropropane can be hydrolysed to propanol, CH3CH2CH2OH, by sodium hydroxide. Write the equation for this reaction | CH3CH2CH2Cl + NaOH → CH3CH2CH2Cl + NaCl |
| Propanol can be dehydrated. It loses a water molecule to form a hydrocarbon. Give the name formula of this hydrocarbon | p |
| Propanol can be dehydrated. It loses a water molecule to form a hydrocarbon. Give the structural formula of this hydrocarbon | CH2=CHCH3; |
| Propanol is oxidised to a carboxylic acid by acidifiedpotassiummanganate Deduce the name of this acid. | p acid |
| Sulfuric acid is an important acid, it is manufactured in the Contact Process. Originally, it was made by heating metal sulfates and by burning a mixture of sulfur and potassium nitrate. Give 4 major uses of sulfuric acid. | Making fertilisers Pickling metals Making fibres Making phosphoric acid |
| When this mineral is heated gently it dehydrates. FeSO4.7H2O - green FeSO4 + 7H2O - pale yellow Describe how you could show that this reaction is reversible | Add water (to yellow solid or to (anhydrous) iron(II) sulfate or to FeSO4 or to products goes green |
| When the iron(II) sulfate is heated strongly, further decomposition occurs. 2FeSO4(s) Fe2O3(s) + SO2(g) + SO3(g) The gases formed in this reaction react with water and oxygen to form sulfuric acid. Explain how the sulfuric acid is formed. | M1 - Sulfur trioxide reacts with water to make sulfuric acid or equation M2 - sulfur dioxide reacts with oxygen to form sulfur trioxide or equation |
| When a mixture of sulfur and potassium nitrate is burned and the products are dissolved in water, sulfuric acid is formed. The sulfuric acid formed by this method is not pure. It contains 3 other acids. Deduce the identity of this acids. | nitric acid nitric(V) acid HNO3 |
| When a mixture of sulfur and potassium nitrate is burned and the products are dissolved in water, sulfuric acid is formed. The heat causes some of the potassium nitrate to decompose. Write the equation for the action of heat on potassium nitrate | 2KNO3 = 2KNO2 + O2 Species Balance |
Created by:
Haridus Academy