Chemistry Chapter 6: Acid, Base and Salt
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Questions and Answers

What is the meaning of 'acid'?

A substance that donates hydrogen ions (H+) in an aqueous solution.

What is the meaning of 'alkali'?

A substance that accepts hydrogen ions or donates hydroxide ions (OH-) in an aqueous solution.

What is the basicity of carbonic acid, H2CO3?

2

What type of water do clownfish require?

<p>Water with pH values between 8.0 to 8.3.</p> Signup and view all the answers

What is pH?

<p>A logarithmic measure of the concentration of hydrogen ions in an aqueous solution.</p> Signup and view all the answers

What is the formula to calculate the pH value of acid?

<p>pH = -log [H+]</p> Signup and view all the answers

How do you calculate the pOH value for an alkali?

<p>pOH = -log [OH-]</p> Signup and view all the answers

The pH value of nitric acid, HNO3 with 0.5 mol dm–3 of hydrogen ions, H+ is _____

<p>0.301</p> Signup and view all the answers

What happens to hydrogen ions in a strong acid?

<p>They ionize completely in water to produce a high concentration of hydrogen ions.</p> Signup and view all the answers

How does concentration of hydrogen ions affect the pH value of an acid?

<p>The higher the concentration of hydrogen ions, the lower the pH value.</p> Signup and view all the answers

What type of acid is acetic acid, CH3COOH?

<p>A weak acid.</p> Signup and view all the answers

Strong acids do not ionize completely in water.

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

PH values below 7 indicate an alkaline solution.

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

What is the chemical formula for ethanoic acid?

<p>CH3COOH</p> Signup and view all the answers

What is the degree of dissociation of ethanoic acid in water?

<p>1.54%</p> Signup and view all the answers

Which of the following ions are produced when ethanoic acid ionizes?

<p>CH3COO–</p> Signup and view all the answers

What is the difference between strong alkalis and weak alkalis?

<p>Strong alkalis ionize completely in water, while weak alkalis ionize partially.</p> Signup and view all the answers

What is the chemical formula for sodium hydroxide?

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

What is the degree of dissociation of ammonia in water?

<p>1.3%</p> Signup and view all the answers

What ions are formed when ammonia ionizes in water?

<p>OH–</p> Signup and view all the answers

What are the physical properties of acids?

<p>Sour taste, turn blue litmus paper red, pH values less than 7.</p> Signup and view all the answers

What do acids produce when they react with bases?

<p>Salt and water.</p> Signup and view all the answers

What is produced when acids react with reactive metals?

<p>Salt and hydrogen gas (H2).</p> Signup and view all the answers

What products are formed when acids react with carbonates?

<p>Salt, water, and carbon dioxide gas (CO2).</p> Signup and view all the answers

What is the chemical equation for the reaction between hydrochloric acid (HCl) and barium hydroxide (Ba(OH)2)?

<p>Barium hydroxide + Hydrochloric acid → Barium chloride + Water</p> Signup and view all the answers

What is the chemical equation for the reaction between hydrochloric acid (HCl) and magnesium (Mg)?

<p>Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen gas</p> Signup and view all the answers

What is the chemical equation for the reaction between hydrochloric acid (HCl) and zinc carbonate (ZnCO3)?

<p>Zinc carbonate + Hydrochloric acid → Zinc chloride + Water + Carbon dioxide gas</p> Signup and view all the answers

Write an equation in words to summarize the reaction of an alkali solution with dilute acids.

<p>Alkali + Acid → Salt + Water</p> Signup and view all the answers

Write an equation in words to summarize the reaction of an alkali solution with ammonium salts.

<p>Alkali + Ammonium salt → Salt + Water + Ammonia gas</p> Signup and view all the answers

Write an equation in words to summarize the reaction of an alkali solution with metal ions.

<p>Alkali + Metal ion → Insoluble metal hydroxide + Cation from alkali</p> Signup and view all the answers

Alkalis react with acids to produce ______ and ______.

<p>salt, water</p> Signup and view all the answers

When a mixture of alkali and ammonium salt is heated, ______ gas is released.

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

Addition of an alkali to most metal ions produces an ______ metal hydroxide precipitate.

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

What is a standard solution?

<p>A solution with known concentration.</p> Signup and view all the answers

How is the concentration of a solution measured?

<p>Concentration is measured in g dm–3 or mol dm–3.</p> Signup and view all the answers

What is the molarity of a solution that contains 10 moles of solute in 5 dm3 of solution?

<p>2.0 mol dm–3</p> Signup and view all the answers

Concentration (g dm–3) = Mass of solute (g) ÷ Volume of solution (dm3)

Signup and view all the answers

If 0.4 mol of zinc chloride (ZnCl2) is dissolved in water to produce 2 dm3 of solution, what is the molarity of the solution?

<p>0.2 mol dm–3</p> Signup and view all the answers

The reaction between HCl(aq) and Ba(OH)2(aq) results in the formation of _____.

<p>BaCl2 + 2H2O</p> Signup and view all the answers

The reaction between H2SO4(aq) and KOH(aq) produces _____.

<p>K2SO4 + 2H2O</p> Signup and view all the answers

The equation for the reaction between HNO3(aq) and NaOH(aq) is _____.

<p>NaNO3 + H2O</p> Signup and view all the answers

Which of the following is true regarding the applications of neutralization?

<p>Milk of magnesia is used to relieve gastric pain.</p> Signup and view all the answers

What are some nutrients that need to be replaced in soil for crop growth?

<p>Nitrogen, potassium, and phosphorus.</p> Signup and view all the answers

What is urea produced from?

<p>Neutralization reaction between ammonia and carbon dioxide.</p> Signup and view all the answers

What is the role of water in showing acidic and alkaline properties?

<p>Water is needed for an acid or alkali to ionise and show its properties.</p> Signup and view all the answers

What is the pH value related to?

<p>The pH value indicates the concentration of hydrogen ions, H+, in a solution.</p> Signup and view all the answers

Acids produce _____ ions when dissolved in water.

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

What defines a monoprotic acid?

<p>A monoprotic acid is defined as an acid that produces one hydrogen ion per molecule.</p> Signup and view all the answers

What happens when hydrogen chloride gas is dissolved in water?

<p>It ionizes to produce hydrogen ions, H+, and chloride ions, Cl–.</p> Signup and view all the answers

What are alkalis?

<p>Alkalis are bases that are soluble in water and produce hydroxide ions, OH–.</p> Signup and view all the answers

All bases are alkalis.

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

What is formed when an acid reacts with a base?

<p>A salt and water are formed.</p> Signup and view all the answers

Which of the following is an example of a diprotic acid?

<p>Sulfuric Acid, H2SO4</p> Signup and view all the answers

What is a standard solution?

<p>A standard solution is a solution of known concentration used in titrations.</p> Signup and view all the answers

What do stalactites and stalagmites form from?

<p>They form from the precipitation of calcium carbonate, CaCO3.</p> Signup and view all the answers

The chemical formula for sodium hydroxide is _____?

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

What is the aim of Activity 6.7?

<p>To prepare 250 cm3 of standard solution of 1.0 mol dm–3 sodium carbonate, Na2CO3.</p> Signup and view all the answers

What materials are needed for preparing the standard solution?

<p>Distilled water and solid sodium carbonate, Na2CO3.</p> Signup and view all the answers

What is the first step in the procedure for preparing the solution?

<p>Determine the mass of sodium carbonate, Na2CO3 needed using the formula n = MV.</p> Signup and view all the answers

Why must the beaker and filter funnel be rinsed with distilled water?

<p>To ensure that all of the sodium carbonate solution is transferred without contamination.</p> Signup and view all the answers

What is the significance of aligning the meniscus level with the calibration mark?

<p>To ensure the accurate volume of solution is measured.</p> Signup and view all the answers

Why does the volumetric flask need to be closed after preparation of the standard solution?

<p>To prevent contamination and ensure that the solution remains homogenous.</p> Signup and view all the answers

What happens when sodium carbonate, Na2CO3 is dissolved in distilled water?

<p>It produces bicarbonate ions and hydroxide ions.</p> Signup and view all the answers

What formula is used to calculate the molarity during dilution?

<p>M1V1 = M2V2</p> Signup and view all the answers

What is the molarity of the copper(II) sulfate solution prepared by diluting 25 cm3 of 2.0 mol dm–3 solution to 500 cm3?

<p>0.1 mol dm–3.</p> Signup and view all the answers

Sodium hydroxide, NaOH, is suitable for preparing a standard solution.

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

What is defined as neutralisation in chemistry?

<p>A reaction between an acid and an alkali to produce salt and water.</p> Signup and view all the answers

Study Notes

Acid, Base and Salt

  • Basicity of acids determines the number of hydrogen ions (H+) that an acid can produce when dissolved in water.
  • Monoprotic acids release one H+ ion (e.g., Hydrochloric acid, HCl), diprotic acids release two H+ ions (e.g., Sulfuric acid, H2SO4), and triprotic acids release three H+ ions (e.g., Phosphoric acid, H3PO4).
  • Water is essential for acids to exhibit acidic properties; without it, solid acids do not ionize to produce H+ ions, and indicators like litmus paper do not change color.
  • Bases are substances that react with acids to produce salt and water, typically categorized into soluble bases (alkalis) and insoluble bases.
  • A base that dissolves in water produces hydroxide ions (OH−). Common examples include Sodium hydroxide (NaOH) and Potassium hydroxide (KOH).
  • Neutralization occurs when an acid and a base react to form water and salt, illustrated by the reaction of Ca(OH)2 and HNO3 to produce Ca(NO3)2 and water.

pH Value and Properties

  • The pH scale measures acidity and alkalinity, with lower values (below 7) indicating acids and higher values (above 7) indicating alkalis.
  • The presence of hydrogen ions (H+) correlates with acidic properties, while hydroxide ions (OH−) correlate with alkaline properties.
  • Salts are formed from the neutralization reaction of an acid with a base and can be further categorized into soluble and insoluble salts.

Uses and Applications

  • Acids and bases are prevalent in daily life; for example, vinegar is acidic and used in cooking, while toothpaste is alkaline and helps neutralize acid in the mouth.
  • Standard solutions are prepared with a known concentration of a solute, often used in titrations to determine the concentration of an unknown solution.
  • Titration is a laboratory technique that uses a standard solution to quantify the concentration of another solution, typically involving an acid-base reaction.

Laboratory Concepts

  • Insoluble salts can be formed through chemical reactions, such as double decomposition reactions.
  • Recrystallization is a method used to purify solid compounds by dissolving them in a suitable solvent and allowing them to crystallize.
  • Qualitative analysis involves determining the presence of certain ions or compounds within a sample without measuring their amounts.

Environmental Impact

  • Formation of stalactites and stalagmites in limestone caves results from the interaction of carbonic acid in rainwater with calcium carbonate (CaCO3), leading to calcium bicarbonate as an intermediate step.

Safety Considerations

  • Acids and bases can be corrosive; proper safety measures, including wearing gloves and goggles, are essential when handling these substances in a laboratory setting.### pH and Its Importance
  • pH is a logarithmic measure of hydrogen ion concentration in an aqueous solution, described by the formula: pH = –log [H+].
  • pH scale ranges from 0 (acidic) to 14 (alkaline), with 7 being neutral.
  • Solutions with pH < 7 are acidic, while those with pH > 7 are alkaline.
  • Clownfish thrive in water with a pH between 8.0 to 8.3, indicating a preference for alkaline conditions.

Calculating pH

  • pH can be calculated using the concentration of hydrogen ions, [H+].
  • Example: For 0.5 mol dm–3 nitric acid (HNO3), pH = –log [0.5] = 0.301.
  • Example: For hydrochloric acid (HCl) with pH 2.0, [H+] = 10^-2 = 0.01 mol dm–3.

Relationship Between pH and Hydroxide Ions

  • The concentration of hydroxide ions, [OH–], can be used to calculate pOH with pOH = –log [OH–].
  • The relationship between pH and pOH is given by: pH + pOH = 14.
  • Example: For sodium hydroxide (NaOH) with [OH–] = 0.1 mol dm–3, pOH = –log [0.1] = 1; thus, pH = 14 - 1 = 13.

Strength of Acids and Bases

  • Strong acids completely ionize in water, yielding a high concentration of hydrogen ions (e.g., HCl).
  • Weak acids partially ionize, resulting in a lower concentration of hydrogen ions (e.g., CH3COOH).
  • The degree of ionization is critical in determining the strength of an acid or base.

Strong and Weak Alkalis

  • Strong alkalis completely dissociate in water to produce hydroxide ions (e.g., NaOH).
  • Weak alkalis only partially dissociate (e.g., NH3), producing fewer hydroxide ions.

Empirical Studies on pH

  • Experiments can demonstrate the relationship between hydrogen ion concentration and pH.
  • It is hypothesized that higher hydrogen ion concentration results in lower pH values for acids.
  • For alkalis, a similar relationship exists wherein higher hydroxide ion concentration leads to higher pH values.

Daily Life Applications

  • Common household substances have various pH values, which can be tested using indicators.
  • Activities include measuring the pH of items like soap water, milk tea, lime juice, and carbonated drinks.

Conclusion from Experiments

  • The relationship between ion concentration, pH values, and acids/bases is observable through empirical data.
  • Changes in acid or alkali concentration directly influence their pH and consequently their acidity or alkalinity.### Ammonia Ionisation
  • Ammonia (NH3) reacts with water (H2O) to partially ionise, forming ammonium ions (NH4+) and hydroxide ions (OH–).

Strength of Acids and Alkalis

  • Use online simulations to observe the dissociation of acids and bases, adjusting acid strength to evaluate hydrogen ions (H+) and hydroxide ions (OH–) present.
  • The degree of dissociation correlates with the concentration of H+ and OH– ions.

Definitions of Acids and Alkalis

  • Strong Acid: Completely dissociates in solution, producing a high concentration of H+ ions.
  • Weak Acid: Only partially dissociates, resulting in lower H+ ion concentration.
  • Strong Alkali: Completely dissociates to yield a high concentration of OH– ions.
  • Weak Alkali: Partially dissociates, leading to fewer OH– ions.

pH Comparison of Acids

  • A 0.1 mol dm–3 solution of nitric acid (HNO3) has a different pH than oxalic acid (H2C2O4) due to their varying strengths and dissociation characteristics.

Chemical Properties of Acids

  • Acids are characterized by a sour taste, ability to turn blue litmus paper red, and a pH less than 7.
  • Chemically, acids react as follows:
    • With bases to create salt and water.
    • With reactive metals to generate salt and hydrogen gas.
    • With metal carbonates to yield salt, water, and carbon dioxide gas.

Laboratory Activity on Acids

  • Experimentation includes adding copper(II) oxide (CuO) to sulfuric acid (H2SO4), filtering, and evaporating to form salt crystals.
  • Observations include changes in color and state of the reactants, as well as characteristics of the resultant solution and solid.

Chemical Properties of Alkalis

  • Alkalis react similarly to acids, producing salt and water upon reaction with acids.
  • Heating a mixture of alkali and ammonium salt releases ammonia gas (NH3).
  • Adding an alkali to metal ions typically results in an insoluble metal hydroxide precipitate.

Tables Summarizing Reactions

  • Comprehensive tables detailing reactions showcase acetic reactions such as:
    • Acid + Base → Salt + Water
    • Acid + Reactive Metal → Salt + Hydrogen Gas
    • Acid + Metal Carbonate → Salt + Water + Carbon Dioxide Gas
    • Alkali + Acid → Salt + Water
    • Alkali + Ammonium Salt → Salt + Water + Ammonia Gas
    • Alkali + Metal Ion → Insoluble Metal Hydroxide + Cation from Alkali

Key Safety and Laboratory Practices

  • Perform experiments under supervision, with protocols in place for handling reactive substances and managing byproducts safely.
  • Document observations and outcomes methodically in reports during experimental activities.

Discussion Questions for Reflection

  • Identify changes and colors in reactions, understand gaseous byproducts, and articulate the outcomes in chemical equations to reinforce learning.

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Form 4 Chemistry Textbook - Acid, Base and Salt PDF

Description

Explore the fundamental concepts of acids, bases, and salts in this quiz based on Chapter 6. You will learn about pH, strength of acids, and various reactions such as neutralization and titration. Dive into the properties and behaviors of these essential chemical compounds.

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