Chapter 3 chemistry II

Question: Why is CO2 gas at room tempe- rature while SiO2 is solid?

Answer: In CO2, there are two dipoles in each molecule. Two dipoles are equal and opposite, so they cancel each other. Therefore net dipole moment of CO2 is zero. Due to non polar nature, there is no force of attraction between molecules of CO2. Hence CO2 is a gas.

In SiO2, each silicon atom is bonded to 4 oxygen atoms and each oxygen is bonded to the two Silicon atoms in a tetrahedral shape. This arrangement is repeated throughout the crystal. Thus, three dimensional structure gives a crystal lattic. Due to this reason, the SiO2 is solid at room temperature.

Question: What is importance of oxides of lead in Paints?

Answer: The oxides of lead have great importance in paints. The lead suboxide (Pb2O) is used in black paint. The lead monoxide is used in yellow paints. The red lead (Pb3O4) is used in red paints. The lead trioxide (Pb2O3) is used in orange colour paints. Moreover, lead chromate, white lead, Chrome yellow, Chrome green are mixed in paints to give designer sheets.

Question: How does borax serve as a water softening agent?

Answer: Borax is used for softening of hard water and it is also used in washing powder. The hard water contain calcium and magnesium ion. When hard water is treated with borax then calcium and magnesium ions are removed as in insoluble borate and water become soft.

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Class 9 Chemistry Notes for Federal Board

Class 9 Chemistry Notes for Federal Board Introduction Class 9 Chemistry notes for the Federal Board have been written according to the National Curriculum 2006. It develops various skills such as questioning, observations, predicting, measuring, classifying, designing experiments, analyzing and interpreting the data. among students. We have made these notes very simple. After reading these notes, students can easily understand all topics. Students can answer all types of questions including essay type, short and multiple choice, self assessments and think tank. We have also solved exercises according to the Federal board examination pattern. Students, after going through 9th class chemistry notes can get maximum marks in their exams. They can lay down a strong foundation of scientific knowledge among students. In future, notes for class 9 will be available in pdf format. Students will be able to note pdf free download very soon. Students will have access to these notes in a mobi

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Class 10 Chemistry Notes for Federal Board Introduction Class 10 Chemistry Notes for Federal Board have been written according to the National Curriculum 2006. These notes will make students able to learn topics by their own. 10th class notes for all chapters are very and easy to understand. After studying these notes, students will become confident to answer all type of questions. Chemistry notes for class 10 provide solution to all kinds of questions including essay type, short and multiple choice, self assessments and think tank. These notes also contain all past papers of reduced syllabus as well as complete syllabus. Soon, students will have access to 10th class chemistry notes in Urdu pdf download form. We are also working hard to provide all chemistry notes in pdf format and student will be able to download these notes. We also trying to upload video lectures about class 10 chemistry. Don't forget, you can test your chemistry by using online test. Furthermore, you highl

Theories of Covalent Bonding and Shapes of Molecules: MCQs

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Chemistry

T he Federal Board of Intermediate & Secondary Education (FBISE) is an autonomous body that conducts the examinations in the institutions affiliated with it in Pakistan as well as abroad. Punjab government has ten boards of Intermediate & Secondary Education including Bahawalpur Board, D.G. Khan Board, Faisalabad Board, Gujranwala Board, Lahore Board, Multan Board, Rawalpindi Board and Sargodha Board and each board conducts exams independently. Federal Board generally follows the international norms and standards. Federal Board paper pattern is quite tricky and similar to O-Level and A Level formats. These questions need conceptual approach to be solved. Punjab board’s Paper pattern is comparatively easy up to some extent. We are currently focusing on the subject of Chemistry for all classes affiliated with Federal Board ( IX , X , XI , XII ) and Punjab Board ( XI XII ). We intend to extend it to all subjects in future. After reading All Student Notes, studen

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CHAPTER # 15 ORGANIC COMPOUNDS

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