On heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O2 and a brown gas X is formed.
(a) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ?
(b) Dry hydrogen chloride gas does not change the colour of dry litmus paper. Why ?
How is sodium hydroxide manufactured in industries ? Name the process. In this process a gas X is formed as by-product. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reactions involved.
List in tabular form three distinguishing features between autotrophic nutrition and heterotrophic nutrition.
What is carpel ? Write the function of its various parts.
A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 18 cm. Find the nature, position and size of the image formed.
Write the essential function performed by ozone at the higher levels of the Earth’s atmosphere ? How is it produced ? Name the synthetic chemicals mainly responsible for the drop of amount of ozone in the atmosphere. How can the use of these chemicals be reduced ?
What are solar cells ? Explain the structure of solar panel. List two principal advantages associated with solar cells.
The electrons in the atoms of four elements A, B, C and D are distributed in three shells having 1, 3, 5 and 7 electrons respectively in their outermost shells. Write the group numbers in which these elements are placed in the Modern Periodic Table. Write the electronic configuration of the atoms of B and D and the molecular formula of the compound formed when B and D combine.
List any three observations which posed a challenge to Mendeleev’s Periodic Law.
Consider the given circuit and find the current flowing in the circuit and potential difference across the 15 Ω resistor when the circuit is closed.
Calculate the equivalent resistance of the following network :
A teacher provided acetic acid, water, lemon juice, aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3, 12, 4, 8 and 14 respectively. Which one of these values is not correct ? Write its correct value stating the reason.
What would a student report nearly after 30 minutes of placing duly cleaned strips of aluminium, copper, iron and zinc in freshly prepared iron sulphate solution taken in four beakers ?
What is observed when a pinch of sodium hydrogen carbonate is added to 2 mL of acetic acid taken in a test tube ? Write chemical equation for the reaction involved in this case.
After examining a prepared slide under the high power of a compound microscope, a student concludes that the given slide shows the various stages of binary fission in a unicellular organism. Write two observations on the basis of which such a conclusion may be drawn.
List in proper sequence four steps of obtaining germinating dicot seeds.
List four precautions which a student should observe while preparing a temporary mount of a leaf peel to show stomata in his school laboratory.
The current flowing through a resistor connected in a circuit and the potential difference developed across its ends are as shown in the diagram by milliammeter and voltmeter readings respectively:
Describe Economic Hardships Faced By Europe In 1830s?
Describe the serious problem faced by the modern part of Hanoi in 1903.
How had the printing press created a new culture of reading in Europe ? Explain with examples.
How had Charles Dickens depicted the terrible effects of industrialisation on peoples lives and characters ? Explain with examples.
Describe any three main features of ‘Alluvial soil’ found in India.
‘‘The dams that were constructed to control floods have triggered floods.’’ Analyse the statement.
Name any two subjects that are included in Concurrent List. How are laws made on these subjects ? Explain.
How is sharing of power between the Union and the State Governments basic to the structure of the Constitution of India ? Explain.
Every social difference does not lead to social division.’’ Justify the statement.
‘‘Crude oil reserves are limited all over the world. If people continue to extract it at the present rate, the reserves would last only 35 - 40 years more.’’ Explain any three ways to solve this problem.
Why is it necessary to increase a large number of banks mainly in rural areas ? Explain.
Why are service conditions of formal sector loans better than informal sector ? Explain.
How can the Government of India play a major role to make globalisation more fair ? Explain with examples.
How has globalisation affected the life of Indians ? Explain with examples.
How are consumers enjoying the ‘right to be informed’ in their daily life ? Explain with examples.
How had the ‘First World War’ created economic problems in India ? Explain with examples.
How had a variety of cultural processes developed a sense of collective belongingness in India during the 19th century ? Explain with examples.
Describe the role of ‘technology’ in transformation of the world in the nineteenth century.
Describe the life of workers during the nineteenth century in England.