Chemistry Applications: pH and Ohm's Law
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Questions and Answers

Why is maintaining an optimal pH range crucial for crops in agriculture?

  • To enhance the soil's color.
  • To prevent soil erosion.
  • To increase the soil's density.
  • To ensure effective nutrient absorption. (correct)
  • What could be a consequence of pH imbalance in the human body?

  • Enhanced physical strength.
  • Increased metabolic rate.
  • Development of certain diseases. (correct)
  • Improved cognitive functions.
  • What range of pH is generally considered safe for drinking water?

  • Between 6.5 and 8.5 (correct)
  • Between 9.5 and 10.5
  • Between 10.5 and 12.5
  • Between 4.5 and 5.5
  • How does pH affect food preservation?

    <p>It prevents microbial growth. (A)</p> Signup and view all the answers

    According to Ohm's Law, what is the relationship between current (I) and resistance (R) when the voltage (V) is kept constant?

    <p>Current is inversely proportional to resistance. (C)</p> Signup and view all the answers

    What is the key difference between specific conductance and equivalent conductance?

    <p>Specific conductance is per unit length and cross-sectional area, while equivalent conductance relates to one gram equivalent of electrolyte. (B)</p> Signup and view all the answers

    In a dry cell, what is the role of manganese dioxide ($MnO_2$)?

    <p>To act as a depolarizer, preventing hydrogen gas buildup. (A)</p> Signup and view all the answers

    A scientist wants to test the acidity of three unknown solutions (X, Y, and Z) using a new, highly sensitive pH meter. Due to a lab mishap, the meter is now only able to provide readings in a relative, rather than absolute, scale. The meter indicates that X is 'more acidic than Y', and Y is 'less acidic than Z'. Based solely on these readings, which of the following statements must be true?

    <p>Solution X has the lowest pH among the three. (B)</p> Signup and view all the answers

    Signup and view all the answers

    Flashcards

    pH in Agriculture

    The pH of soil affects plant growth, with optimal pH typically 6-7 for nutrient absorption.

    Safe pH for Drinking Water

    Drinking water should have a pH between 6.5 and 8.5 for safety.

    pH Effects on Food

    pH affects food preservation, taste, and texture; fermented products depend on specific pH levels.

    pH and Human Body

    Normal blood pH in humans is around 7.4; imbalances can lead to diseases.

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    Ohm's Law

    Current through a conductor is proportional to voltage and inversely proportional to resistance (V=IR).

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    Specific Conductance

    The ability of a solution to conduct electricity per unit length and area; reciprocal of resistivity.

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    Equivalent Conductance

    Conductance of one gram equivalent of an electrolyte in a solution.

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    Dry Cell

    A primary, non-rechargeable cell that converts chemical energy to electrical energy; used in many devices.

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    Study Notes

    pH Value Applications

    • Agriculture and Soil Science: Soil pH impacts plant growth. Crops thrive in a pH range of 6-7 for optimal nutrient uptake. Acidic soil is treated with lime (CaCO3), while alkaline soil is treated with gypsum.

    • Medicine and Human Body: Normal human blood pH is around 7.4. Imbalance in pH can lead to health issues.

    • Water Quality and Industry: Safe drinking water pH ranges from 6.5 to 8.5. Industrial processes (electroplating, dyeing, papermaking) require precise pH control.

    • Food and Beverages: pH affects food preservation, taste, and texture. Fermented foods (like curd, vinegar) rely on specific pH levels. Acidic pH (soft drinks, pickles) inhibits microbial growth.

    Ohm's Law

    • Ohm's Law states that current through a conductor is directly proportional to the applied voltage, and inversely proportional to the resistance.
    • The formula is: V = IR (Voltage = Current x Resistance)

    Specific and Equivalent Conductance

    • Specific Conductance: Measures a solution's ability to conduct electricity per unit length and cross-sectional area. It is the reciprocal of resistivity (k = 1/ρ). Units are Siemens per meter (S/m).

    • Equivalent Conductance: Measures the conductance of one gram equivalent of an electrolyte in solution.

    Dry Cell

    • Description: A non-rechargeable primary cell that converts chemical energy to electrical energy via a redox reaction. Used in various devices (torches, clocks, radios).

    • Construction:

      • Outer zinc container is the anode (negative terminal).
      • Electrolyte paste (mixture of ammonium chloride and zinc chloride) facilitates ion conduction.
      • Graphite rod (carbon electrode) is the cathode (positive terminal).
      • Manganese dioxide and carbon powder surround the graphite rod act as a depolarizer.
    • Advantages: Compact, portable, provides steady voltage (approximately 1.5 V), no leakage.

    • Disadvantages: Non-rechargeable, limited lifespan, voltage drops over time.

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    Description

    Explore the applications of pH in agriculture, medicine, water quality, and food science, along with an introduction to Ohm's Law and its significance in electrical circuits. This quiz will test your understanding of how these concepts impact various fields and daily life.

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