Description : 13. A ray of light, incident obliquely on a face of a rectangular glass slab placed in air, emerges from the opposite face parallel to the incident ray. State two factors on which the lateral displacement of the emergent ray depends. [Foreign] -Chemistry-10
Last Answer : Lateral displacement depends on the: angle of incidence, thickness of slab, and refractive index of the material. (any two)
Description : What are metalloids? Explain by giving examples. -Chemistry-10
Last Answer : Metalloids are elements which show some properties of metals and some properties of non-metals. Examples: Silicon, boron, arsenic, antimony, germanium, tellurium, polonium.
Description : What happens when baking soda is heated? -Chemistry-10
Last Answer : Sodium hydrogen carbonate (also known as sodium bicarbonate or bicarbonate of soda) has the chemical formula NaHCO3. When it is heated above about 80°C it begins to break down, forming sodium carbonate, water and carbon dioxide. This type of reaction is called a thermal decomposition.
Description : Why is plaster of paris stored in a moisture proof container? -Chemistry-10
Last Answer : Plaster of Paris in contact with moisture (water) changes to solid hard mass, gypsum. Therefore, it gets wasted. Hence it should be stored in moisture proof containers.
Description : (i) Substances oxidised is Na as it gains oxygen and oxygen is reduced. (ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen. -Chemistry-10
Last Answer : During this reaction, the sodium is gaining oxygen and is being oxidized. Oxygen is getting reduced. During this reaction, copper oxide is losing oxygen and is being reduced. The hydrogen is gaining oxygen and is being oxidized.
Description : Identify the substances that are oxidised and the substances which are reduced in the following reactions. (i) 4Na(s) + O2(g) → 2Na2O(s) (ii) CuO (s) + H2(g) → Cu (s) + H2O(l) -Chemistry-10
Last Answer : (i) Substances oxidised is Na as it gains oxygen and oxygen is reduced. (ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen.
Description : Give an example of a double displacement reaction other than the one given in Activity 1.10 -Chemistry-10
Last Answer : Sodium hydroxide and hydrochloric acid react to form sodium chloride and water.
Description : An iron nail is dipped in the solution of copper sulphate for about 30 minutes. State the change in colour observed. Give reason for the change. -Chemistry-10
Last Answer : When an iron nail is dipped in copper sulphate solution, the displacement reaction takes place. The colour of copper sulphate solution fades due to the formation of light green solution of iron sulphate.
Description : Why does the colour of copper sulphate solution change when an iron nail is dipped in it ? -Chemistry-10
Description : Why is the amount of gas collected in one of the test tubes in text book Activity 1.7 (i.e., electrolysis of water) double of the amount collected in the other? Name this gas. -Chemistry-10
Last Answer : In Activity 1.7, water is electrolysed to give H2 gas at one electrode and O2 gas at the other electrode. 2H2O(l) → 2H2(g) + O2(g) Thus two molecules of water on electrolysis give two ... oxygen gas or in other words the amount of hydrogen gas collected would be double than that of oxygen gas.
Description : A solution of a substance ‘X’ is used for white washing. (i) Name the substance ‘X’ and write its formula. (ii) Write the reaction of the substance ‘X’ named in (i) above with water. -Chemistry-10
Last Answer : (i) The substance whose solution in water is used for white washing is calcium oxide (or quick lime). Its formula is CaO.
Description : Write a balanced chemical equation with state symbols for the following reactions : -Chemistry-10
Last Answer : (i) BaCl2 (aq) + Na2SO4 (aq) → BaSO4(s) + 2NaCl (aq) (ii) NaOH (aq) + HCl(aq) → NaCl(aq) + H2O(l)
Description : Write the balanced equation for the following chemical reactions. (i) Hydrogen + Chlorine → Hydrogen chloride (ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride (iii) Sodium + Water → Sodium hydroxide + Hydrogen -Chemistry-10
Last Answer : (i) H2 + Cl2 → 2HCl (ii) 3 BaCl2 + Al2(SO4)3 → BaSO4 + 2 AlCl3 (iii) 2Na + 2H2O → 2NaOH + H2↑
Description : 15. An object 2 cm high is placed at a distance of 64 cm from a white screen. On placing a convex lens at a distance of 32 cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the conve -Chemistry-10
Last Answer : Since, object-screen distance is double of object-lens separation, the object is at a distance of 2f from the lens and the image should be of the same size of the object.
Description : 14. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the -Chemistry-10
Last Answer : Answer. hope this helps you
Description : 12. Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed: -Chemistry-10
Description : 10. Which kind of mirrors are used in the headlights of a motor-car and why? [Foreign] -Chemistry-10
Last Answer : Answer. Concave mirror, to get the parallel beam of light.
Description : 11. Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface. [Delhi] -Chemistry-10
Last Answer : Answer. Light from different points on the pencil, immersed in water refracts and appears to come from a point above the original position.
Description : 7. Redraw the given diagram and show the path of the refracted ray: [All India(C)] -Chemistry-10
Description : 6. “The refractive index of diamond is 2.42”. What is the meaning of this statement in relation to speed of light? [Delhi] -Chemistry-10
Description : 5. The refractive indices of four media A, B, C and D are given in the following table: -Chemistry-10
Last Answer : (i) Minimum change is seen as light moves between 1.50 and 1.52, i.e. B and C. (ii) Maximum change when light moves between 1.33 and 2.40, i.e. A and D.
Description : 4. If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. [Delhi (C)] -Chemistry-10
Last Answer : Answer. Ray NQ, as it has to be parallel to ray OS.
Description : 3. Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed: -Chemistry-10
Last Answer : Answer. Nature of image: Real, inverted and same size image is formed at the centre of curvature. Nature of image: Virtual, enlarged and erect image is formed behind the mirror. Nature of image: ... image: Virtual, erect and diminished image is formed between O and F on the same side of object.
Description : 2. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. [All India] -Chemistry-10
Last Answer : this is the answer for the respected question
Description : 1. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. [Delhi] -Chemistry-10
Last Answer : Answer. hope this helps youu
Description : Magnesium ribbon on burning in air produces a) magnesium oxide ,water and light c) magnesium oxide and heat b) magnesium oxide , heat and light d) magnesium oxide, water and heat
Last Answer : b) magnesium oxide , heat and light
Description : You are provided with magnesium ribbon and sulpher powder. Explain with the help of an activity that metal oxides are basic and non-metal oxide are acidic in nature. -Chemistry
Last Answer : Aim: To test the nature of oxides formed by metals and non-metals. Materials Required: Sulphur powder, Mg ribbon, water, blue litmus paper, red litmus paper. Procedure: 1.Take magnesium ribbon ... the metallic oxides are basic in nature whereas most of the non-metallic oxides are acidic in nature.
Description : .Identify the physical and chemical changes from the following (i)Burning of magnesium in air (ii)Electrolysis of water (iii)Tarnishing of silver spoon (iv)Sublimation of iodine -Chemistry
Last Answer : (i) Burning of magnesium in air : Chemical change (ii) Tarnishing of silver spoon : Chemical change (iii) Sublimation of iodine : Physical change (iv) Electrolysis of water to form hydrogen and oxygen is also a chemical change.
Description : Which compound is formed when a Magnesium ribbon is burnt in air? (1) Magnesium Nitrate (2) Magnesium Carbonate (3) Magnesium Oxide (4) Magnesium Nitride
Last Answer : (3) Magnesium Oxide Explanation: When Magnesium burns air it reacts with oxygen present in air to form magnesium oxide.
Description : A piece of magnesium ribbon was heated to redness in an atmosphere of nitrogen and then cooled with water. The gas evolved is
Last Answer : A piece of magnesium ribbon was heated to redness in an atmosphere of nitrogen and then cooled with ... . ammonia B. hydrogen C. nitrogen D. oxygen
Description : Is Magnesium ribbon burns leaving white ash?
Last Answer : Need answer
Description : Give reason: Magnesium ribbon should not be kept near bottles containing volatile chemicals.
Last Answer : Magnesium is a reactive metal therefore it should not be kept near bottles containing volatile chemicals.
Description : The displacement reaction between iron (III) oxide and a metal X is used for welding the rail tracks. Here X is: (a) Copper granules (b) Magnesium ribbon (c) Sodium pellets (d) Aluminum dust
Last Answer : (d) Aluminum dust
Description : Is burning magnesium in the air a chemical change?
Last Answer : Yes. Burning anything is a chemical change.
Description : Write chemical equation reactions taking place when carried out with the help of (a) Iron reacts with steam (b) Magnesium reacts with dil HCl (c) Copper is heated in air. -Chemistry
Last Answer : This is the Answer.
Description : State the type of chemical reactions and chemical equations that take place in the following: (i) Magnesium wire is burnt in air. (ii) Electric current is passed through water. (iii) Ammonia and hydrogen chloride gases’are mixed. -Chemistry
Last Answer : This is the Answer:
Description : Dust content in raw blast furnace gas is about __________ gm/Nm3 ; hence it is cleaned to the dust level of about < 10 mg /Nm3 before use. (A) 15-30 (B) 1-2 (C) 70-100 (D) 150-200
Last Answer : (A) 15-30
Description : Is the burning of magnesium in oxygen?
Description : Why do the number of particles stay the same after burning magnesium?
Last Answer : Feel Free to Answer
Description : Give reason: During burning of magnesium not only magnesium oxide is formed but also magnesium nitride is formed.
Last Answer : Due to high temperature the triple bond between nitrogen atoms is broken and a small quantity of magnesium nitride is formed.
Description : During burning of magnesium, we should wear sun glasses to protect our eyes from white dazzling light as it: (a) damage the retina (b) leads to loss of our vision (c) both (a) & (b) (d) none of these
Last Answer : (c) both (a) & (b)
Description : Write balanced equation for the reaction between magnesium and hydrochloric acid. Name the product obtained, identify the type of reaction. -Chemistry
Last Answer : Answer. The product formed is magnesium chloride and hydrogen gas. It is a displacement reaction.
Description : You are given samples of three metals. Sodium, magnesium and copper. Suggest any two activities to arrange them in order of decreasing activity. -Chemistry
Last Answer : Activity 1: Sodium reacts with cold water vigorously to form sodium hydroxide and hydrogen gas Magnesium does not react with cold water but with hot water to form magnesium ! hydroxide and hydrogen gas. Hence sodium is more reactive than magnesium.
Description : Define the term valency. What is the valency for magnesium and copper? -Chemistry 9th
Last Answer : The no.of electrons required for the element to be octate or duplate is known as valency. Magnesium = 2 Copper = 1 hope this helps u
Description : (a) Define a balanced chemical equation. Why should an equation be balanced? (b) Write the balanced chemical equation for the following reaction: (i) Phosphorus burns in presence of chlorine to form phosphorus penta chloride. (ii) Burning of natural gas. (iii) The process of respiration. -Chemistry
Last Answer : Answer. (a) Balanced chemical equation has an equal number of atoms of different elements in the reactants and products. According to law of conservation of mass, matter can neither be created nor be destroyed in a chemical ... C6H12O6 (s) + 6O2 (g) + 6H2O ---> 6CO2 (aq) + 12H2O (l) + energy
Description : (Follow-up Q) How many times do you wear an item of clothing that is "dry-clean only" before you actually get it cleaned?
Last Answer : Oh, that means you actually have to have it cleaned at some point?
Description : The sprayers are cleaned before use by— (A) 1% chlorine water (B) 1% hydrochloric acid (C) 1% ammonia water (D) 1% bromine water
Last Answer : (B) 1% hydrochloric acid
Description : When was the last time that you cleaned or changed your air-distribution unit/system filter?
Last Answer : I wash mine every new season, so 4 times a year. Doing it on a specific date helps remind me to clean it. I have no idea about your other questions, but I have a really good air/heating guy that even comes on Sundays and doesn’t charge extra.
Description : How many times a year should house air ducts be cleaned?
Last Answer : My house has forced air heating. How often should the air duct cleaning be performed?
Description : Controller contacts should be routinely cleaned by ________. A. blowing with compressed air B. filing with a bastard file C. wiping with a clean dry cloth D. dressing with crocus cloth
Last Answer : Answer: C