Give reasons why copper is used to make hot
[question] Question. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron). [/question] [solution] solution: Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react vigorously with the steam formed from hot water. [/solution]...
Differentiate between metal and non-metal on the
[question] Question. Differentiate between metal and non-metal on the basis of their chemical properties. [/question] [solution] solution: Metals (i) Metals are electropositive. (ii) They react with oxygen to form basic oxides. (iii) These have ionic bonds. (iv) They react with water to form oxides and hydroxides. Some metals react with cold water, some with hot water, and some with steam. (v) They react with dilute acids to form a salt and evolve hydrogen gas. However, $\mathrm{Cu}$, Ag, Au, Pt...
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice.
[question] Question. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels. [/question] [solution] solution: Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in the lemon or tamarind neutralises the basic copper carbonate and dissolves the lay...
Give reasons.
[question] Question. Give reasons. (a)Platinum, gold and silver are used to makejewellery. (b)Sodium, potassium and lithium are stored under oil. (c)Aluminium is a highly reactive metal, yet it is used to make utensils for cooking. (d)Carbonate and sulphide ores are usually converted into oxides during the process of extraction. [/question] [solution] solution: (a)Platinum, gold, and silver are used to make jewellery because they are very lustrous. Also, they are very less reactive and do not co...
What type of oxides is formed when non-metals
[question] Question. What type of oxides is formed when non-metals combine with oxygen? [/question] [solution] solution: Non-metals combine with oxygen to form acidic oxides. For example, [/solution]...
State two ways to prevent the
[question] Question. State two ways to prevent the rusting of iron. [/question] [solution] solution: Two ways to prevent the rusting of iron are- (i) Oiling, greasing, or painting- By applying oil, grease, or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented. (ii) Galvanisation - An iron article is coated with a layer of zinc metal, which prevents the iron to come in contact with oxygen and...
In the electrolytic refining of a metal M,
[question] Question. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte ? [/question] [solution] solution: In the electrolytic refining of a metal M Anode – Impure metal M Cathode – Thin strip of pure metal M Electrolyte – Acidified solution of salt of the metal M [/solution]...
Name two metals which will displace hydrogen from dilute acids,
[question] Question. Name two metals which will displace hydrogen from dilute acids, and two metals which will not. [/question] [solution] solution: Metals that are more reactive than hydrogen displace it from dilute acids. For example- sodium and potassium. Metals that are less reactive than hydrogen do not displace it. For example- copper and silver. [/solution]...
What are amphoteric oxides ?
[question] Question. What are amphoteric oxides ? Give two examples of amphoteric oxides. [/question] [solution] solution: Those oxides that behave as both acidic and basic oxides are called amphoteric oxides. Examples- Aluminium oxide $\left(\mathrm{Al}_{2} \mathrm{O}_{3}\right)$, Zinc oxide $(\mathrm{ZnO})$ [/solution]...
You are given a hammer,
[question] Question. You are given a hammer, a battery, a bulb, wires and a switch. (a) How could you use them to distinguish between samples of metals and non-metals? (b) Assess the usefulness of these tests in distinguishing between metals and non-metals. [/question] [solution] solution: (a)With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is malleable), then it is a metal otherwise a non metal. Similarly, we can use the battery, bulb, wires, and a s...
Food cans are coated with tin and not with zinc because
[question] Question. Food cans are coated with tin and not with zinc because (a)zinc is costlier than tin. (b)zinc has a higher melting point than tin. (c)zinc is more reactive than tin. (d)zinc is less reactive than tin. [/question] [solution] solution: (c)Food cans are coated with tin and not with zinc because zinc is more reactive than tin. [/solution]...
An element reacts with oxygen to give a compound with a high melting point.
[question] Question. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be (a) Calcium (b) Carbon (c) Silicon (d) Iron [/question] [solution] solution: (a) The element is likely to be calcium [/solution]...
Which of the following methods is suitable for preventing
[question] Question. Which of the following methods is suitable for preventing an iron frying pan from rusting? (a) Applying grease (b) Applying paint (c) Applying a coating of zinc (d) all of the above. [/question] [solution] solution: (c) Applying a coating of zinc (We can also apply grease and paint to prevent iron from rusting. However, in case of iron frying pan, grease and paint cannot be applied because when the pan will be heated and washed again and again, the coating of grease and pain...
Which of the following pairs will
[question] Question. Which of the following pairs will give displacement reactions ? (a) NaCl solution and copper metal (b) $\mathrm{MgCl}_{2}$ solution and aluminium metal (c) $\mathrm{FeSO}_{4}$ solution and silver metal (d) $\mathrm{AgNO}_{3}$ solution and copper metal. [/question] [solution] solution: (d) $\mathrm{AgNO}_{3}$ solution and copper metal [/solution]...
What are alloys ?
[question] Question. What are alloys ? [solution] solution: Alloys are homogeneous mixtures of two or more elements. The elements could be two metals, or a metal and a non-metal. An alloy is formed by first melting the metal and then dissolving the other elements in it. For example, steel is an alloy of iron and carbon. [/solution]...
Which metals do not corrode
[question] Question. Which metals do not corrode easily ? [/question] [solution] solution: More reactive a metal is, more likely it is to be corroded. Therefore, less reactive metals are less likely to get corroded. This is why gold plating provides high resistance to corrosion. [/solution]...
Metallic oxides of zinc, magnesium and copper
[question] Question. Metallic oxides of zinc, magnesium and copper were heated with the following metals. In which cases will you find displacement reactions taking place? [solution] solution: [/solution]...
What chemical process is used for obtaining
[question] Question. What chemical process is used for obtaining a metal from its oxide ? [/question] [solution] solution: The chemical process used for obtaining a metal from its oxide is reduction. In this process, metal oxides are reduced by using suitable reducing agents such as carbon or by using highly reactive metals to displace the metals from their oxides. For example, zinc oxide is reduced to metallic zinc by heating with carbon. $\mathrm{ZnO}(\mathrm{s})+\mathrm{C}(\mathrm{s}) \stackr...
Name two metals which are
[question] Question. Name two metals which are found in nature in the free state. [/question] [solution] solution: The metals at the bottom of the reactivity series are mostly found in free state. For examplegold, silver, and platinum. [/solution]...
Define the following terms.
[question] Question. Define the following terms. (i) Mineral (ii) Ore (iii) Gangue [/question] [solution] solution: (i) Mineral: Most of the elements occur in nature in combined state as minerals. The chemical composition of minerals is fixed. (ii) Ore : Minerals from which metals can be extracted profitably are known as ores. (iii) Gangue: The impurities (sand, silt, soil, gravel,etc.) present in the ore are called gangue. [/solution]...
Why do ionic compounds have high
[question] Question. Why do ionic compounds have high melting points? [/question] [solution] solution: Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces. That is why ionic compounds have high melting points. [/solution]...
(i) Write the electron-dot structures for sodium, oxygen and magnesium.
[question] Question. (i) Write the electron-dot structures for sodium, oxygen and magnesium. (ii) Show the formation of $\mathrm{Na}_{2} \mathrm{O}$ and $\mathrm{MgO}$ by the transfer of electrons. (iii) What are the ions present in these compounds? [/question] [solution] solution: (i) The representation of elements with valence electrons as dots around the elements is referred to as electron-dot structure for elements. (iii) The ions present in $\mathrm{Na}_{2} \mathrm{O}$ are $\mathrm{Na}^{+}$...
What would you observe when zinc is added to a solution of iron
[question] Question. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place. [/question] [solution] solution: Zinc is more reactive than iron. Therefore, if zinc is added to a solution of iron (II) sulphate, then it would displace iron from the solution and green colour of $\mathrm{FeSO}_{4}$ solution will fade. $\mathrm{Zn}(\mathrm{s})+\mathrm{FeSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_{4}(\mathrm{aq})+\mathrm{Fe}(\mathr...
Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
[question] Question. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute $\mathrm{H}_{2} \mathrm{SO}_{4}$. [/question] [solution] solution: Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal. When iron reacts with dilute $\mathrm{H}_{2} \mathrm{SO}_{4}$, iron (II) sulphate with the evolution of hydrogen gas is formed. $\mathrm{Fe}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\math...
Samples of four metals A, B, C and D
[question] Question. Samples of four metals A, B, C and D were taken and added to the following solutions one by one. The results obtained have been tabulated as follows. Use the above table to answer the following questions about metals A, B, C and D. (i) Which is the most reactive metal? (ii) What would you observe if B is added to a solution of copper (II) sulphate ? (iii) Arrange the metals A, B, C and D in the order of decreasing reactivity. [/question] [solution] solution: $\mathrm{A}+\mat...
Write equations for the reactions of
[question] Question. Write equations for the reactions of (i) Iron with steam (ii) Calcium and Potassium with water [/question] [solution] solution: [/solution]...
Why sodium is kept immersed
[question] Question. Why sodium is kept immersed in kerosene oil ? [/question] [solution] solution: Sodium and potassium are very reactive metals and combine explosively with air as well as water. Hence, they catch fire if kept in open. Therefore, to prevent accidental fires and accidents, sodium is stored immersed in kerosene oil. [/solution]...
Explain the meaning of malleable
[question] Question. Explain the meaning of malleable and ductile. [/question] [solution] solution: Malleable: Substances that can be beaten into thin sheets are called malleable. For example, most of the metals are malleable. Ductile: Substances that can be drawn into thin wires are called ductile. For example, most of the metals are ductile. [/solution]...
Give an example of a metal which
[question] Question. Give an example of a metal which (i) is a liquid at room temperature. (ii) can be easily cut with a knife. (iii) is the best conductor of heat. (iv) is a poor conductor of heat. [/question] [solution] solution: (i) Metal that exists in liquid state at room temperature – Mercury (ii) Metal that can be easily cut with a knife – Sodium (iii) Metal that is the best conductor of heat – Silver (iv) Metals that are poor conductors of heat –Mercury and lead [/solution]...