Class-6 Subject Science Chapter-12 Electricity & Circuits

EVENTS CONVENT HIGH SCHOOL

30/10/2021      CLASS- 6     SESSION 2021-22
SUBJECT : SCIENCE

CHAPTER-12
ELECTRICITY & CIRCUITS

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1. Fill in the blanks:
(a) A device that is used to break an electric circuit is called_______________
(b) An electric cell has___________
Ans:
(a) switch
(b) two

2. Mark ‘True’ or ‘False’ for the following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermocol.
Ans:
(a) True
(b) False
(c) False.

VERY SHORT ANSWER TYPE QUESTIONS

1. What is the direction of flow of current in a dry cell?
Ans: . The current flows in closed circuit from +ve to -ve terminal of cell.

2. Name the +ve terminal of dry cell.
Ans:. Carbon rod with a metal cap on it.

3. Name the -ve terminal of a dry cell.
Ans:  Zinc metal plate.

4. What is dry cell?
Ans:  It is a device which converts chemical energy into electrical energy.

5. What is solar cell?
Ans: A device which converts solar energy into electrical energy.

6. What is open circuit?
Ans:  An electric circuit in which electrical contact at any point is broken is called open circuit.

7. Write one use of insulators.
Ans: Insulators are used in making switchboard, handles of testers, screw drivers.

8. What is the name of thin wire in the electric bulb?
Ans: Filament.

Class 6 Science Chapter 12 SHORT ANSWER TYPE QUESTIONS

1. Mention two advantages of a dry cell.
Ans: 
1. It converts chemical energy into electrical energy.
2. It is light and small in size.

2. Draw a diagram showing the two terminals of a bulb.
Ans:

3. Draw the circuit diagram for operating a bulb with the help of a dry cell.
Ans:

4. Define conductors and insulators. Give one example of each.
Ans:  A conductor is that which easily allows the passage of current through it. Example: Aluminium or any metal.
An insulator is that which does not allow the passage of current through it. Example: Rubber.

5. Identify conductors and insulators from the following:Eraser, paper, matchstick, copper wire, pencil lead, polythene
Ans: Conductors: Copper wire, pencil lead.
Insulator. Eraser, paper, matchstick, polythene.

6. Name the scientist who invented electric cell and the scientist who invented electric bulb.
Ans: Electric cell: Alessandro Volta.
Electric bulb: Thomas Alva Edison.

7. Give one activity to prove that air is an insulator.
Ans: Take an electric circuit, keep the terminals unconnected in the air. The bulb do not glow, as air is an insulator and does not allow the current to flow through it.

8. In any electric circuit, when the switch is on and the current flows through it why do the wire, switches, bulb or devices become hot?
Ans.: This is because electric energy changes into heat energy.

9.The headlights of a car have reflectors behind the bulb. What is the function of reflectors?
Ans: The reflector helps in reflecting the light into a focussed area.

10.If you touch an electric wire carrying current you get a shock, but if on the same wire the birds sit they do not get any shock/current. Explain why?
Ans: When we hold the wire carrying current then the circuit is closed and the current flows from our body and enters earth but the birds sitting on the same wire do not get any current as the circuit is not complete. If the bird touches the earth wire, it will also die due to electric shock.

LONG ANSWER TYPE QUESTIONS

1.(1)What is electric circuit?
(2)How many types of electric circuit are there? Define them.
(3)Draw a diagram to show the closed circuit for switch, bulb and dry cell.
Ans: 
(1)The diagram that shows the path of electric current is called electric circuit.
(2)There are two types of electric circuit:
(a) Open electric circuit
(b) Closed electric circuit
(a)Open electric circuit: The circuit in which electrical contact at any point is broken is called open electric circuit.
(b)Closed electric circuit: The circuit in which electric current flows from one terminal of a cell or battery to the other is called a closed circuit.

CLASS-9 SUBJECT-HINDI CHAPTER-12 कैदी और कोकिला

 EVENTS CONVENT HIGH SCHOOL

27/10/2021      CLASS- 9     SESSION 2021-22
SUBJECT : HINDI

CHAPTER-12

कैदी और कोकिला

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पाठ्यपुस्तक के प्रश्न-अभ्यास

प्रश्न 1.कोयल की कूक सुनकर कवि की क्या प्रतिक्रिया थी?
उत्तर-
कोयल की कूक सुनकर कवि को लगा कि वह मानो उसे कुछ कहना चाहती है। या तो वह उसे निरंतर लड़ते रहने की प्रेरणा देना चाहती है या उसकी यातनाओं के दर्द को बाँटना चाहती है। उसे लगता है कि कोकिल कवि के कष्टों को देखकर आँसू बहा रही है और चुपचाप अँधेरे को बेधकर विद्रोह की चेतना जगा रही है। इसलिए अंत में कवि उसके इशारों पर आत्म-बलिदान करने को तैयार हो जाता है।

प्रश्न 2.कवि ने कोकिल के बोलने के किन कारणों की संभावना बताई?
उत्तर-
कवि ने कोकिल के बोलने पर निम्नलिखित कारणों की संभावना जताई है-

• कोयल जेल में बंद क्रांतिकारियों को देशवासियों की दुर्दशा के बारे में बताने आयी है।
• कोयल कैदी क्रांतिकारियों को धैर्य बँधाने एवं दिलासा देने आई है।
• कोयल कैदी क्रांतिकारियों के दुखों पर मरहम लगाने आई है।
• कोयल पागल हो गई है जो आधी रात में चीख रही है।

प्रश्न 3.किस शासन की तुलना तम के प्रभाव से की गई है और क्यों?
उत्तर-
ब्रिटिश शासन की तुलना तम के प्रभाव से की गई है।
क्यों ब्रिटिश शासकों ने बेकसूर भारतीयों पर घोर अत्याचार किए। उन्होंने स्वतंत्रता सेनानियों को कारागृह में तरह-तरह की यातनाएँ दीं। उन्हें कोल्हू के बैल की तरह जोता गया।

प्रश्न 4.कविता के आधार पर पराधीन भारत की जेलों में दी जाने वाली यंत्रणाओं का वर्णन कीजिए।
उत्तर-
पराधीन भारत की जेलों में भारतीयों को पशुओं की भाँति-रखा जाता था। उन्हें ऐसी यातनाएँ दी जाती थीं कि सुनकर ही रोंगटे खड़े हो जाते हैं। इनमें से कुछ निम्नलिखित हैं-

• उन्हें ऊँची-ऊँची दीवार वाली जेलों में रखा जाता था।
• उन्हें दस फुट की छोटी-छोटी कोठरियों में रखा जाता था।
• उन्हें भरपेट खाना नहीं दिया जाता था।
• उनके साथ पशुओं-सा व्यवहार किया जाता था।
• उन्हें बात-बात पर गालियाँ दी जाती थीं।
• उन्हें तड़प-तड़पकर मरने के लिए छोड़ दिया जाता था।

प्रश्न 5.भाव स्पष्ट कीजिए
(क) मृदुल वैभव की रखवाली-सी, कोकिल बोलो तो!
(ख) हूँ मोट खींचता लगा पेट पर जूआ, खाली करता हूँ ब्रिटिश अकड़ का कुँआ।
उत्तर-
(क) कवि के अनुसार, वैसे तो संसार में कष्ट-ही-कष्ट हैं। यदि कहीं कुछ मृदुलता और सरसता बची है तो वह कोयल के मधुर स्वर में बची है। अतः कोयल मृदुलता की रखवाली करने वाली है। वह उससे पूछता है कि आखिर वह जेल में अपना मधुर स्वर गुँजाकर उसे क्या कहना चाहती है!

(ख) इसमें जेल की असहनीय यातनाएँ झेलता हुआ कवि स्वाभिमानपूर्वक कहता है कि वह अपने पेट पर कोल्हू का जूआ बाँधकर चरसा चला रहा है। आशय यह है कि उससे पशुओं जैसा सख्त काम लिया जा रहा है। फिर भी वह हार नहीं मान रहा। इससे ब्रिटिश सरकार की अकड़ ढीली पड़ रही है। अंग्रेज़ों को बोध हो गया है कि अब अत्याचार करने से भी वे सफल नहीं हो सकते।

प्रश्न 6.अर्धरात्रि में कोयल की चीख से कवि को क्या अंदेशा है?
उत्तर-
आधी रात में कोयल की चीख सुनकर कवि को यह अंदेशा होता है कि उसने भारतीयों के आक्रोश एवं असंतोष की ज्वाला देख ली होगी। यह ज्वाला जंगल में लगने वाली आग के समान भयंकर रही होगी। कोयल उसी ज्वाला (क्रांति) की सूचना देने जेल परिसर के पास आई है।

प्रश्न 7.कवि को कोयल से ईष्र्या क्यों हो रही है?
उत्तर-
कवि को कोयल से इसलिए ईर्ष्या हो रही है क्योंकि कोयल स्वतंत्र है, जबकि कवि बंदी है। कोयल हरियाली का आनंद ले रही है, जबकि कवि दस फुट की अँधेरी कोठरी में जीने के लिए विवश है। कोयल के गान की सभी सराहना करते हैं, जबकि कवि के लिए रोना भी गुनाह हो गया है।

प्रश्न 8.कवि के स्मृति-पटल पर कोयल के गीतों की कौन सी मधुर स्मृतियाँ अंकित हैं, जिन्हें वह अब नष्ट करने पर तुली है?
उत्तर-
कवि के स्मृति पटल पर कोयल की कर्णप्रिय अत्यंत मधुर स्वर की स्मृतियाँ अंकित हैं, जिन्हें अब वह नष्ट करने पर तुली है।

प्रश्न 9.हथकड़ियों को गहना क्यों कहा गया है?
उत्तर-
गहना उस आभूषण को कहते हैं, जो धारणकर्ता का गौरव और सौंदर्य बढ़ाए। पं. माखनलाल चतुर्वेदी जैसे क्रांतिकारी, जिन्होंने स्वतंत्रता प्राप्ति के लिए स्वयं प्रेरणा से संघर्ष का मार्ग अपनाया था, जेल को अपना प्रिय आवास तथा हथकड़ियों को गहना समझते थे। उन्हें किसी गलत कार्य के लिए हथकड़ी नहीं पहननी पड़ी। उन्होंने स्वतंत्रता प्राप्ति के महान उद्देश्य के लिए हथकड़ियाँ स्वीकार कीं, अतः उनसे उनका गौरव बढ़ा। समाज ने उन्हें उन हथकड़ियों के लिए प्रतिष्ठा दी। इसलिए उन्होंने हथकड़ियों को गहना कहा।

प्रश्न 10.‘काली तू …. ऐ आली!’-इन पंक्तियों में ‘काली’ शब्द की आवृत्ति से उत्पन्न चमत्कार का विवेचन कीजिए।
उत्तर-
‘काली तू … ऐ आली!’ इन पंक्तियों में काली शब्द की आवृत्ति हुई है। इस शब्द का अर्थ भी उसके संदर्भानुसार है। संदर्भ के अनुसार काली शब्द के निम्नलिखित अनेक अर्थ हैं-

• हथकड़ियाँ रात, कोयल आदि का रंग काला बताने के लिए।
• अंग्रेजों के अन्यायपूर्ण कारनामें बताने के लिए।
• पराधीन भारतीयों का भविष्य अंधकारमय बताने के लिए।
• अंग्रेज़ों के प्रति भारतीयों के मन में उठने वाले आक्रोश के संबंध में।

CLASS-6 SUBJECT:HISTORY CHAPTER-9 TRADERS AND PILGRIMS

 EVENTS CONVENT HIGH SCHOOL

27/10/2021      CLASS- 6     SESSION 2021-22
SUBJECT : HISTORY

CHAPTER-9
TRADERS KINGS AND PILGRIMS

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I. MULTIPLE CHOICE QUESTIONS

(i) Puhar was an important port on the

(a) West coast
(b) East coast
(c) Malabar coast
(d) None of the above.

(ii) The most fertile river valley was
(a) Kaveri
(b) the Yamuna
(c) Ganga
(d) None of the above.

(iii) The capital of the Pandyas was
(a) Madurai
(b) Mudumalai
(c) Patliputra
(d) Ujjain.

(iv) The Satavahanas became an Important dynasty In
(a) Northern India
(b) Eastern India
(c) Southern India
(d) Western India

(v) The rulers who ruled over central Asia and north-west India around 2000 years ago were
(a) Pandyas
(b) Cholas
(c) Kushanas
(d) Cheras.

Answer:
(a) – (b), (iii) – (a), (iii) – (a), (iv) – (d), (v) – (c).

II. FILL IN THE BLANKS

Fill in the blanks with appropriate words to complete each sentence.

1. Gold, ………  and ……….. were in abundance in South India.
2. Gautamiputra Shri Satakami and other Satavahana rulers were known as lords of the …………
3. The famous Kushana ruler ………….. organized a Buddhist council.
4. The older form of Buddhism was known as ……………..
5. Buddha’s attainment of enlightenment was shown by sculptures of the ………………………tree.
6. Anyone could follow the path of………………
7. Xuan Zang, a Chinese Buddhist pilgrim took the………………… route to return to China.
8. …….. was the most famous Buddhist monastery.
9. The two major centres of power of the Kushanas were ………………..  and ………….
10. The images of deities were placed within special homes or places known as

Answer: 

1. spices, precious stones
2. dakshinapatha
3. Kanishka
4. Kanishka
5. peepal
6. Bhakti
7. land
8. Nalanda
9. Peshawar, Mathura
10. temples.

III. TRUE/FALSE

State whether these sentences are true (T) or false (F).

1. FaXran started his journey back home from Nalanda.
2. Pepper, a very important spice grown in South India was known as black gold in the Roman Empire.
3. Muvendar is a Bengali word meaning three chiefs.
4. Puhar or Kaveripaltinam was the port of the Pandyas.
5. The statues of Buddha were made in Mathura and Taxila.
6. Bodhisattvas were persons who had attained enlightenment.

Answer:

1. False
2. True
3. False
4. False
5. True
6. True.

IV.MATCHING SKILL

Match the items in column A correctly with those given in column B.Column B


Ans. (i)—(b), (ii)—(d), (iii)—(a), (iv)—(e), (v)—(c).

V.VERY SHORT ANSWER TYPE QUESTIONS

1. Where can evidence of trade be found?
Ans: Evidence of trade can be found in the Sangam poems.

2. What was South India famous for? [Imp.]
Ans: It was famous for items like gold and precious stones and spices like pepper. Q. 3. How can you say that Rome had a flourishing trade with south India?Ans. Many Roman gold coins have been found in south India.

4. Name the three ruling families of south India
Ans: The Cholas, Cheras and Pandyas.

5. How did the chiefs use the tribute that they collected from neighbouring areas?
Ans: They kept some of the wealth for their use and distributed the rest amongst their supporters.

6. Who were the supporters of the chiefs?
Ans: Their family members, soldiers and poets.

7. Name the items that the chiefs gave to the poets as a reward.
Ans: Precious stones, gold, horses, elephants, chariots and fine cloth.

QUESTIONS

1. Who was Gautamiputra Shri Satakami? How do we come to know about him?[Imp.]
Ans: Gautamiputra Shri Satakami was the famous ruler of the Satavahana dynasty. We come to know about him from an inscription composed by his mother. According to this inscription he and other Satavahana rulers were known as lords of the dakshinapatha, which was used as a name for the entire southern region. He sent his army to the eastern, western, and southern coasts

2. How did the knowledge of silk spread far and wide?                                      [V. Imp.]
Ans: China was the first country where silk took its birth. Although the country kept the-methods of making silk a closely guarded secret for a long time, people of other regions ultimately came to know about them.

• Some people from China went to distant lands on foot, horseback, and camels and with them they carried silk.
• Sometimes, Chinese rulers sent gifts or silk to rulers in Iran and West Asia. From there the knowledge of silk spread further west.

3. Why was silk so expensive? [Imp.]
Ans: Silk had to be brought from China. It was a long journey and the traders had to cross dangerous roads through mountains and deserts. People living along the route often demanded payments from the traders for giving them permission to pass through.

4. Write a brief note on the Chinese Buddhist pilgrims.
Ans: Fa Xran, Xuan Zang and I-Qing were the famous Chinese Buddhist pilgrims who came to India to visit places associated with the life of the Buddha. They also visited famous monasteries. These pilgrims left an account of their journey. They mentioned the dangers that they had to face on their way to monasteries that they visited. They also mentioned the books that they carried with them. These pilgrims also carried with them the statues of the Buddha.

5. What was the Bhakti system of belief? [V. Imp.]
Ans:  According to the Bhakti system of belief, if a devotee worships the chosen deity with a pure heart, the deity will appear in the form in which he/she may desire. Therefore, the deity could be thought of as a human being, lion, tree or any other form. Once this idea gained acceptance, artists made beautiful images of these deities.

CLASS-7 SUBJECT-SOCIAL SCIENCE HISTORY CHAPTER-5 RUELRS AND BUILDINGS

EVENTS CONVENT HIGH SCHOOL

26/10/2021      CLASS- 7     SESSION 2021-22
SUBJECT :HISTORY

CHAPTER-5
RULERS & BUILDINGS

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Very Short Answer Type Questions

1. Why was limestone cement used in the construction of large structures? [V. Imp.]
Answer: Limestone cement was very high-quality cement, which, when mixed with stone chips hardened into concrete. This made the construction of large structures easier and faster.

2. How did the Persian court chronicles describe the Sultan?
Answer: Persian court chronicles described the Sultan as the ‘Shadow of God’.

3. Name the ruler who won universal respect for constructing a large reservoir just – outside Delhi-i kuhna?
Answer: Sultan Iltutmish.

4. What are the special features of Humayun’s tomb?
Answer: (a) It has a central towering dome.
(b)It has a tall gateway (pishtaq).

5. What was maha mandapa?
Answer: It was the main hall in the temple where dances were performed.

6. Name the temple built by king Rajarajadeva.
Answer: Rajarajeshvara temple.

7. When was the tomb of Hanuman built?
Answer: It was built between 1562 and 1571.

8. Who constructed the Kandariya Mahadeva temple?
Answer: King Dhangadeva of the Chandela dynasty constructed the Kandariya Mahadeva temple.

9. Where was Shah Jahan’s capital in the early years of his reign?
Answer: It was at Agra

1o. What is the special feature of Fatehpur Sikri, Akbar’s capital?
Answer: Many of the buildings show the influence of the architectural styles of Gujarat and Malwa.

11. Name the king who invaded Sri Lanka? Whom did he defeat?
Answer: King Shrimara Shrivallabha. He defeated the king, Sena I.

12. What was havellis?
Answer: They were large mansions of the merchants.

13. How did kings win the praise of their subjects? [V. Imp.]
Answer: They won the praise of their subjects by buildings structures meant for a public activity such as temples, mosques, tanks, wells, caravanserais, and bazaars.

Short Answer Type Questions

1. What type of structures were built by kings and their officers between the eighth and the eighteenth centuries? 
Answer: During this period kings and their officers built two kinds of structure
(A)Forts, palaces, garden residences and tombs
(B)Structures meant for public activity including temples, mosques, tanks, wells, caravanserais and bazaars.

2. Write a short note on the Kandariya Mahadeva temple.
Answer: The Kandariya Mahadeva temple dedicated to Shiva was constructed in 999 by the king Dhangadeva of the Chandela dynasty. The temple had an ornamented gateway that led to an entrance. It had the main hall known as maha mandapa where dances were performed. The image of the chief deity was kept in the main Shrine known as garbhagriha. This was the place for ritual worship where only the king and his kith and kin gathered.

3. Throw light on how the construction of the Rqjarqjeshvara temple was a very difficult task.                           [V. Imp.]
Answer: The Raj raj Ishvara temple was built in the early 11th century. It had the tallest shikhara amongst temples of its time. Its construction was a very difficult task. There were no cranes in those days. The 90 tonne stone for the top of the shikhara was too heavy to lift manually. Hence, the architects built an inclined path to the top of the temple, placed the boulder on rollers and rolled it all the way to the top. The path started more than 4 km away so that it would not be too steep. This was dismantled after the temple was built.

4. In what ways do you think the policies of Rajendra I and Mahmud of Ghazni were a product of their time? How were the actions of the two rulers different? [Imp.]
Answer: King Rajendra I looted the temples of the defeated rulers and seized prized statues from them. He these statues in the decoration of the Shiva temple, that he built in his capital in the early 11th century.
Sultan Mahmud of Ghazni was a contemporary of Rajendra I. He destroyed and looted the temples of defeated kings in order to win credit as a great hero of Islam. Thus, King Rajendra, I constructed a temple while Mahmud of Ghazni destroyed it. In this way, their actions were very much different.

5. Write a brief note on the Chahar bagh built by the Mughal rulers.
Answer: The Mughal emperors were very much interested in literature, art, and architecture. Babur, in his autobiography, described his interest in planning and laying out formal gardens, placed within rectangular walled enclosures, and divided into four quarters by artificial channels. These gardens were called Chahar bagh, four gardens, because of their symmetrical division into quarters. Beginning with Akbar, some of the most beautiful Chahar baghs were constructed by Jahangir and Shah Jahan in Kashmir, Agra and Delhi.

6. When was Humayun’s tomb built? What are its special features?
Answer:  Humayun’s tomb was, built between 1562 and 1571. Its main features are:

• The central towering dome and the tall gateway known as pishtaqbecame important aspects of Mughal architecture. This tomb architecture was first visible in Humayun’s tomb.
• The tomb was placed in the centre of a huge formal Chahar baghand built in the tradition known as ‘eight paradises’ or hasht bihisht—a central hall surrounded by eight rooms.
• The building was constructed with red sandstone, edge with white marble.

CLASS-10 SUBEJCT SCIENCE CHAPTER-3 ATOMS AND MOLECULES

 EVENTS CONVENT HIGH SCHOOL

27/10/2021      CLASS-10     SESSION 2021-22
SUBJECT :SCIENCE

CHAPTER-3 aTOMS & MOLECULES

______________________________________

NCERT Textbook for Class 9 Science – Page 32
Question 1. In a reaction 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass carbonate.
Answer.

Class 9 Science NCERT Textbook Page 32
Question 1. In a reaction 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium etkanoate. Show that these observations are in agreement with the law of conservation of mass carbonate.
Answer:

Question 2. Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer: Ratio of H : O by mass in water is:
Hydrogen : Oxygen —> H2O
∴ 1 : 8 = 3 : x
x = 8 x 3
x = 24 g
∴ 24 g of oxygen gas would be required to react completely with 3 g of hydrogen gas.

Question 3. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Answer: The postulate of Dalton’s atomic theory that is the result of the law of conservation of mass is—the relative number and kinds of atoms are constant in a given compound. Atoms cannot be created nor destroyed in a chemical reaction.

Question 4. Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Answer: The relative number and kinds of atoms are constant in a given compound.

Class 9 Science NCERT Textbook Page 35
Question 1. Define the atomic mass unit.
Answer: One atomic mass unit is equal to exactly one-twelfth (1/12th) the mass of one atom of carbon-12. The relative atomic masses of all elements have been found with respect to an atom of carbon-12.

Question 2. Why is it not possible to see an atom with naked eyes?
Answer: Atom is too small to be seen with naked eyes. It is measured in nanometres.
1 m = 109 nm

NCERT Textbook Questions – Page 39
Question 1. Write down the formulae of
(i) Sodium oxide
(ii) Aluminium chloride
(iii) Sodium sulphide
(iv) Magnesium hydroxide
Answer: The formulae are

Question 2. What is meant by the term chemical formula?
Answer: The chemical formula of the compound is a symbolic representation of its composition, e.g., chemical formula of sodium chloride is NaCl.

Question 3. How many atoms are present in a
(i) H2S molecule and
(ii) P043- ion?
Answer: (i) H2S —> 3 atoms are present
(ii) P043- —> 5 atoms are present

NCERT Textbook Questions – Page 40
Question 1. Calculate the molecular masses of H2, O2, Cl2, C02, CH4, C2H2,NH3, CH3OH.
Answer: The molecular masses are:

Question 2.Calculate the formula unit masses of ZnO, Na2O, K2C03, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
Answer: The formula unit mass of
(i) ZnO = 65 u + 16 u = 81 u
(ii) Na2O = (23 u x 2) + 16 u = 46 u + 16 u = 62 u
(iii) K2C03 = (39 u x 2) + 12 u + 16 u x 3
= 78 u + 12 u + 48 u = 138 u

Class 9 Science NCERT Textbook Page 42
Question 1. If one mole of carbon atoms weigh 12 grams, what is the mass (in grams) of 1 atom of carbon?
Answer:

Question 2. Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given atomic mass of Na = 23 u, Fe = 56 u)?
Answer:

Questions From NCERT Textbook for Class 9 Science

Question 1. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
Answer: Boron and oxygen compound —> Boron + Oxygen
0.24 g —> 0.096 g + 0.144 g

Question 2. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
Answer: The reaction of burning of carbon in oxygen may be written as:

It shows that 12 g of carbon bums in 32 g oxygen to form 44 g of carbon dioxide. Therefore 3 g of carbon reacts with 8 g of oxygen to form 11 g of carbon dioxide. It is given that 3.0 g of carbon is burnt with 8 g of oxygen to produce 11.0 g of CO2. Consequently 11.0 g of carbon dioxide will be formed when 3.0 g of C is burnt in 50 g of oxygen consuming 8 g of oxygen, leaving behind 50 – 8 = 42 g of O2. The answer governs the law of constant proportion.

Question 3. What are poly atomic ions? Give examples.
Answer: The ions which contain more than one atoms (same kind or may be of different kind) and behave as a single unit are called polyatomic ions e.g., OH–, SO42-, CO32-.

Question 4. Write the chemical formulae of the following:
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.
Answer: (a) Magnesium chloride
Symbol —> Mg Cl
Change —> +2 -1
Formula —> MgCl2
(b) Calcium oxide
Symbol —> Ca O
Charge —> +2 -2
Formula —> CaO
(c) Copper nitrate
Symbol —> Cu NO
Change +2 -1
Formula -4 CU(N03)2
(d) Aluminium chloride
Symbol —> Al Cl
Change —> +3 -1
Formula —> AlCl3
(d) Calcium carbonate
Symbol —> Ca CO3
Change —> +2 -2
Formula —> CaC03

Question 5. Give the names of the elements present in the following compounds:
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Answer: (a) Quick lime —> Calcium oxide
Elements —> Calcium and oxygen
(b) Hydrogen bromide
Elements —> Hydrogen and bromine
(c) Baking powder —> Sodium hydrogen carbonate
Elements —> Sodium, hydrogen, carbon and oxygen
(d) Potassium sulphate
Elements —> Potassium, sulphur and oxygen

Question 6. Calculate the molar mass of the following substances.
(a) Ethyne, C2H2
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4 (Atomic mass of phosphorus = 31)
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3
Answer: The molar mass of the following: [Unit is ‘g’]
(a) Ethyne, C2H2 = 2 x 12 + 2 x 1 = 24 + 2 = 26 g
(b) Sulphur molecule, S8 = 8 x 32 = 256 g
(c) Phosphorus molecule, P4=4 x 31 = i24g
(d) Hydrochloric acid, HCl = 1 x 1 + 1 x 35.5 = 1 + 35.5 = 36.5 g
(e) Nitric acid, HN03 = 1 x 1 + 1 x 14 + 3 x 16 = 1 + 14 + 48 = 63 g

Question 7. What is the mass of
(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
(c) 10 moles of sodium sulphite (Na2S03)?
Answer: (a) Mass of 1 mole of nitrogen atoms = 14 g
(b) 4 moles of aluminium atoms
Mass of 1 mole of aluminium atoms = 27 g
∴ Mass of 4 moles of aluminium atoms = 27 x 4 = 108 g
(c) 10 moles of sodium sulphite (Na2SO3)
Mass of 1 mole of Na2SO3 = 2 x 23 + 32 + 3 x 16 = 46 + 32 + 48 = 126 g
∴ Mass of 10 moles of Na2SO3 = 126 x 10 = 1260 g

Question 8. Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of Carbon dioxide.
Answer: (a) Given mass of oxygen gas = 12 g
Molar mass of oxygen gas (O2) = 32 g
Mole of oxygen gas 12/32 = 0.375 mole
(b) Given mass of water = 20 g
Molar mass of water (H2O) = (2 x 1) + 16 = 18 g
Mole of water = 20/18 = 1.12 mole
(c) Given mass of Carbon dioxide = 22 g
Molar mass of carbon dioxide (CO2) = (1 x 12) + (2 x 16)
= 12 + 32 = 44 g
∴ Mole of carbon dioxide = 22/44 = 0.5 mole

Question 9. What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Answer: (a) Mole of Oxygen atoms = 0.2 mole
Molar mass of oxygen atoms = 16 g
Mass of oxygen atoms = 16 x 0.2 = 3.2 g
(b) Mole of water molecule = 0.5 mole
Molar mass of water molecules = 2 x 1 + 16= 18 g .
Mass of H2O = 18 x 0.5 = 9 g

Question 10. Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.
Answer: Molar mass of S8 sulphur = 256 g = 6.022 x 1023 molecule
Given mass of sulphur = 16 g

Question 11. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide. (Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)
Answer: Molar mass of aluminium oxide Al203
= (2 x 27) + (3 x 16)
= 54 + 48 = 102 g.