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1. (a) In an AP, if a = 50, d = -4 and Sn= 0, then find the value of n.   OR   (b) Find the sum of the first twelve 2-digit multiples of 7, using an AP.  solution:  OR 2. A solid metallic sphere of radius 3 cm is melted and recast into the shape of a solid cylinder of radius 2 cm. Find the height of the cylinder.  SOLUTION:  3. (a) Find the nature of the roots of the quadratic equation   x2-5x + 9 = 0 OR   (b) Write a quadratic equation with roots -3 and 5.  SOLUTION:  OR 4. Find the mode of the following frequency distribution:  SOLUTION: 

1. Humans have innate immunity to protect against pathogens that may enter the gut and food. What are the two barriers that protect the body from such pathogens? explanation: 1. skin- mechanical barrier retard entry of microbes. it has an acidic environment pH of about 3-5 which retards the growth of microbes. 2. mucous membrane: the conjunctivae and the alimentary respiratory and urogenital tract are lined by mucous membranes which wash away invading pathogens. mucous membrane release mucus which has antiviral and antibacterial substances. 2. A patient admitted to ICU was diagnosed to have suffered from myocardial infarction. The condition of the coronary artery is depicted in the image below. Name two bioactive agents and their mode of action that can improve this condition. OR Substantiate by giving two reasons why a holistic understanding of flora and fauna of the cropland is required before introducing an appropriate biocontrol method. explanation: to improve the patient's con...

1. (a) Draw two different possible structures of a saturated hydrocarbon having four carbon atoms in its molecule. What are these two structures of the hydrocarbon having same molecular formula called? Write the molecular formula and the common name of this compound. Also, write the molecular formula of its alkyne.  OR  (b) (i) Write the molecular formula of benzene and draw its structure.   (ii) Write the number of single and double covalent bonds present in a molecule of benzene.   (iii) Which compounds are called alkynes?  Explanation: two possible structures of hydrocarban these structures are called isomers. isomers have the same molecular formula but different structural arrangements. the molecular formula of the alkyne is  OR i) the molecular formula of benzene is  C6H6 ii) there are double bonds and nine single bonds in benzene. iii) Alkynes are organic molecules made of the functional group carbon-carbon triple bonds and are wri...

 1. (a) Write the molecular formula of the following carbon compounds :  (i) Methane  (ii) Propane (b) Carbon compounds have low melting and boiling points. Why?  explanation: a) molecular formula of methane is CH4 and propane is CH3CH2CH3 b) carbon compounds have the weaker intermolecular force of  interactions hence they have lower boiling and melting points 2. The electrons in the atoms of two elements X and Y are distributed in  three shells having 1 and 7 electrons respectively in their outermost  shells.  (a) Write the group numbers of these elements in the Modern Periodic  Table.  (b) Write the molecular formula of the compound formed when X and  Y combine with each other.  (c) Which of the two is electropositive?  explanation: a) element X has 1 electron in the outermost shell hence it belongs to group 1. while element Y has 7 electrons in the outermost shell to become noble gas and complete its octet it requires o...

  Pollution has become a major concern for people all over the world, as it not only affects our health but also the environment. Pollution is defined as the presence or introduction into the environment of substances or energy that cause harm or discomfort to living organisms, including humans. It can take many forms, including air pollution, water pollution, soil pollution, and noise pollution. In this blog, we will explore the different types of pollution and discuss measures that can be taken to control and prevent it. Types of Pollution Air Pollution: Air pollution is caused by the emission of harmful substances into the air, including carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matter. This can be caused by sources such as factories, power plants, transportation, and agriculture. The health effects of air pollution can be severe, including respiratory problems, heart disease, and stroke. Water Pollution: Water pollution occurs when harmful substances a...

The Evolutionary History of Life on Earth The evolution of life on Earth is a complex and fascinating story that spans billions of years. From the first simple microorganisms to the diverse array of species we see today, life on our planet has undergone countless changes and adaptations to survive and thrive in a constantly changing environment. This blog will provide a brief overview of the key events and milestones in the evolutionary history of life on Earth. The Origins of Life The origins of life on Earth are shrouded in mystery, but it is widely believed that life first appeared on our planet around 3.5 to 4 billion years ago. The exact circumstances that led to the emergence of life are not well understood, but scientists believe that the building blocks of life, such as amino acids and nucleotides, may have formed from chemical reactions in the early oceans. These building blocks eventually combined to form the first simple microorganisms, which were the ancestors of all life o...

  pH is a measure of the acidity or alkalinity of a solution, specifically water-based solutions. The pH scale ranges from 0 to 14, with 7 being neutral, below 7 being acidic, and above 7 being alkaline. Understanding pH is important in many fields, including chemistry, biology, agriculture, and environmental science. In this blog, we will explore what pH is, why it is important, and how it is measured. What is pH? pH stands for “potential hydrogen” and is a measure of the concentration of hydrogen ions (H+) in a solution. The more hydrogen ions present in a solution, the more acidic it is. Conversely, the fewer hydrogen ions present in a solution, the more alkaline it is. Neutral solutions have an equal number of hydrogen ions and hydroxide ions (OH-). Why is pH Important? pH is important because it affects the behavior of chemicals and biological systems. For example, the pH of soil affects the growth of plants, while the pH of water affects the survival of aquatic life. A change...