Water, Acids-Bases, and Buffer Systems

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Questions and Answers

What property of water allows it to be an effective solvent?

  • Dipolar nature (correct)
  • High specific heat capacity
  • Low density in solid form
  • High boiling point

Oxygen is less electronegative than hydrogen in a water molecule.

False (B)

What type of bond forms between the oxygen and hydrogen atoms within a water molecule?

Covalent bond

Water is known as the _____ solvent because it can dissolve many types of substances.

<p>universal</p> Signup and view all the answers

Match the following properties of water with their descriptions:

<p>Covalent bond = Bond within a water molecule Hydrogen bond = Bond between water molecules Dipolar molecule = Molecule with partly positive and negative ends Electronegativity = Ability to attract electrons</p> Signup and view all the answers

What role does water play in cellular compartments?

<p>It facilitates the movement of molecules. (A)</p> Signup and view all the answers

Water cannot separate charged molecules.

<p>False (B)</p> Signup and view all the answers

Define the role of water as a universal solvent.

<p>Water dissolves and transports compounds essential for life.</p> Signup and view all the answers

Water plays a role in __________ by dissipating heat.

<p>thermoregulation</p> Signup and view all the answers

Match the following properties of water with their functions:

<p>Solvent = Dissolves compounds Thermal stability = Regulates temperature Chemical reactivity = Participates in reactions Polarity = Separates ions</p> Signup and view all the answers

Which of the following is NOT a function of water?

<p>Creating energy (A)</p> Signup and view all the answers

Water has no role in transporting compounds in the blood.

<p>False (B)</p> Signup and view all the answers

What makes water a good solvent for many substances?

<p>Its polar structure allows it to dissolve ionic and polar substances.</p> Signup and view all the answers

What is the term for substances that do not interact well with water?

<p>Hydrophobic (D)</p> Signup and view all the answers

The cations in ionic substances are attracted to the positive ends of water molecules.

<p>False (B)</p> Signup and view all the answers

What determines the solubility of a substance in a solvent?

<p>Type of solute and solvent, temperature, and pressure.</p> Signup and view all the answers

A solution is a homogenous mixture of a _______ and a _______.

<p>solute, solvent</p> Signup and view all the answers

Match the types of solutions with their examples:

<p>Gas-Gas = Air Gas-Liquid = CO2 in H2O Solid-Liquid = NaCl in H2O Solid-Solid = Steel (Fe + C)</p> Signup and view all the answers

Which of the following factors affects the speed of dissolving?

<p>Temperature (B)</p> Signup and view all the answers

All ionic substances dissolve equally well in water.

<p>False (B)</p> Signup and view all the answers

Define amphiphilic substances.

<p>Substances that have both polar and non-polar regions.</p> Signup and view all the answers

How is weight percentage (w/w) calculated?

<p>Weight of solute in 100 g of solution (D)</p> Signup and view all the answers

An acid can accept hydrogen ions.

<p>False (B)</p> Signup and view all the answers

What does molarity (M) represent in a solution?

<p>Moles of solute in 1L of solution</p> Signup and view all the answers

A 5% NaCl solution contains ______ g of NaCl in 100 mL of solution.

<p>5</p> Signup and view all the answers

Match the following solutions with their components:

<p>37% HCl = 37 g HCl in 100 g solution 5% EtOH = 5 mL EtOH in 100 mL solution 5% NaCl = 5 g NaCl in 100 mL solution 3M NaCH2COOH = 3 mol NaCH2COOH in 1L solution</p> Signup and view all the answers

What is the correct formula for Weight:Volume percentage (w/v)?

<p>Weight of solute in 100 mL solution (A)</p> Signup and view all the answers

An amphoteric substance can only act as an acid.

<p>False (B)</p> Signup and view all the answers

Explain what happens when an acid ionizes.

<p>It produces a proton and a base.</p> Signup and view all the answers

What is the conjugate base of acetic acid?

<p>Acetate (A)</p> Signup and view all the answers

Strong acids partially ionize in water.

<p>False (B)</p> Signup and view all the answers

Define pH.

<p>pH is the negative logarithm to the base 10 of the hydrogen ion concentration.</p> Signup and view all the answers

Bicarbonate (HCO3-) is the conjugate base of ___________ acid.

<p>carbonic</p> Signup and view all the answers

Match the following acids with their conjugate bases:

<p>Acetic acid = Acetate Citric acid = Citrate Bicarbonate = Carbonate Pyruvic acid = Pyruvate</p> Signup and view all the answers

How does the pH in the blood generally range?

<p>7.35 to 7.45 (B)</p> Signup and view all the answers

Buffers are solutions that stabilize pH by combining weak acids and strong bases.

<p>False (B)</p> Signup and view all the answers

What is the effect of adding an acid or base to a buffer system?

<p>It minimizes pH changes.</p> Signup and view all the answers

Flashcards

Water's role as a solvent

Water dissolves many substances due to its dipolar structure.

Dipolar molecule

A molecule with a positive and negative end, like water.

Hydrogen bond

An attraction between a slightly positive hydrogen atom and a slightly negative atom of another molecule (especially oxygen, nitrogen, or fluorine).

Why is water important for dissolving substances?

Water's dipolar nature allows it to dissolve numerous types of compounds, as a result of its polarity and ability to form hydrogen bonds.

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Electronegativity in water

Oxygen is more electronegative than hydrogen, creating a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms.

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Water structure and solubility

Water's structure (polarity) affects its ability to dissolve different substances; polarity allows for interactions with charged molecules.

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Water as a universal solvent

It is the main solvent in living organisms, dissolving and transporting various components within biological systems.

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What water dissolves

Water easily dissolves charged molecules, which is crucial for biological processes.

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Water's role in heat dissipation

Water helps regulate temperature, absorbing and removing heat.

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Water's role in cellular compartments

Water facilitates the movement of molecules within and between cellular compartments.

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Water's role in chemical reactions

Water participates in many chemical reactions, like the dissolving of substances and moving molecules.

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Biological Importance of Water

Water is essential for life due to its solvent properties and impact on temperature regulation within cells and organisms.

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Ionic substance solubility

Ionic substances dissolve in water because water molecules attract the positive and negative ions.

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Hydrophilic

Substances that dissolve easily in water.

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Hydrophobic

Substances that don't dissolve in water.

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Solution

A homogenous mixture of solvent and solute.

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Solvent

The major component of a solution.

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Solute

The minor component of a solution that is dissolved.

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Solubility

The ability of a substance to dissolve in a solvent.

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Weight Percentage (w/w)

The weight of solute in 100g of solution.

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Volume Percentage (v/v)

The volume of solute in 100 mL of solution.

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Weight-Volume Percentage (w/v)

The weight of solute in 100 mL of solution.

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Molarity (M)

Moles of solute in 1 liter of solution.

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Acid

A substance that releases hydrogen ions (protons).

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Base

A substance that accepts hydrogen ions (protons).

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Amphoteric Substance

A substance that can act as both an acid and a base.

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Acid Ionization

Acids release a proton and form a base.

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Conjugate Base

The species formed when an acid loses a proton (H+).

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Acetate

The conjugate base of acetic acid (CH3COOH).

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Citrate

The conjugate base of citric acid.

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Strong Acid

An acid that completely ionizes in water, meaning all its molecules release H+.

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Weak Acid

An acid that only partially ionizes in water, meaning only some molecules release H+.

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pH

A measure of the acidity or alkalinity of a solution, expressed as the negative logarithm to the base 10 of the hydrogen ion concentration.

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Buffer System

A solution containing a weak acid and its conjugate base, or a weak base and its conjugate acid, which helps resist changes in pH.

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Importance of Buffers

Buffers help maintain stable pH levels in biological systems, vital for the proper functioning of enzymes and other biological processes.

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Study Notes

Water, Acids-Bases, and Buffer Systems

  • Learning Objectives:
    • Recognize water structure
    • Relate water structure to solubility
    • Calculate solution concentrations
    • Define acids and bases
    • Describe buffers

Water

  • Water's properties are crucial for understanding biological molecules' interactions.

  • Water structure is important.

Water Composition

  • Total body water (about 60% of body weight in adults)

    • Intracellular fluid (ICF) ~ 40% of body weight
    • Extracellular fluid (ECF) ~ 20% of body weight
      • Plasma ~ 20% of ECF
      • Interstitial fluid ~80% of ECF

  • Composition varies by age.

Water as a Universal Solvent

  • Water is the solvent of life.
  • Dissolves and transports compounds in blood.
  • Moves molecules within and through cell compartments.
  • Separates charged molecules.
  • Dissipates heat (regulates temperature).
  • Participates in chemical reactions.

Solubility

  • Water's polarity is responsible for its role as a solvent.
  • Water dissolves many substances making it "the universal solvent".
  • Ionic substances dissolve in water due to the attraction of ions to water's charged ends.
    • Cations (positive ions) are attracted to the negative ends of water molecules.
    • Anions (negative ions) are attracted to the positive ends of water molecules.
  • Polar molecules can interact with water (hydrophilic).
  • Nonpolar molecules do not interact with water (hydrophobic).
  • Amphipathic molecules have both a polar and a nonpolar region, exhibiting both hydrophilic and hydrophobic behaviors.

Solutions

  • Homogenous mixture of two or more substances.
    • Major component is the solvent
    • Minor component(s) is the solute
  • Types of solutions (gas in gas, Liquid in Liquid, solid in solid etc.)
    • Examples (Air, Saltwater)

Factors Affecting Solubility

  • Type of solute and solvent
  • Temperature
  • Pressure
  • Common ion effect

Factors Affecting Dissolving Speed

  • Temperature
  • Particle size
  • Mixing

Amount of Solute in a Solution

  • Weight Percentage (w/w)

    • Weight of solute in 100g of solution

  • Volume Percentage (v/v)

    • Volume of solute in 100 mL of solution

  • Weight/Volume Percentage (w/v)

    • Weight of solute in 100 mL of solution

  • Molarity (M)

    • Moles of solute in 1L of solution

Acid/Base

  • Acid: releases hydrogen ions
  • Base: accepts hydrogen ions
  • Amphoteric: can do both
  • Acid-base conjugates (acid and its conjugate base) reduce pH change

Buffer Systems

  • Resist pH changes.
  • Consist of weak acid and its conjugate base, or a weak base and its conjugate acid.

Regulation of Blood pH

  • Blood pH values usually range between 7.35 and 7.45
  • Bicarbonate buffer system is important
  • Phosphate buffer plays a role
  • Proteins also act as buffers

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Water, Acids-Bases, and Buffer Systems (2024) PDF

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