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?
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What is pH?
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What is the formula to calculate the pH value of acid?
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How do you calculate the pOH value for an alkali?
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The pH value of nitric acid, HNO3 with 0.5 mol dm–3 of hydrogen ions, H+ is _____
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What happens to hydrogen ions in a strong acid?
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How does concentration of hydrogen ions affect the pH value of an acid?
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What type of acid is acetic acid, CH3COOH?
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Strong acids do not ionize completely in water.
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PH values below 7 indicate an alkaline solution.
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What is the chemical formula for ethanoic acid?
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What is the degree of dissociation of ethanoic acid in water?
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Which of the following ions are produced when ethanoic acid ionizes?
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What is the difference between strong alkalis and weak alkalis?
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What is the chemical formula for sodium hydroxide?
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What is the degree of dissociation of ammonia in water?
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What ions are formed when ammonia ionizes in water?
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What are the physical properties of acids?
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What do acids produce when they react with bases?
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What is produced when acids react with reactive metals?
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What products are formed when acids react with carbonates?
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What is the chemical equation for the reaction between hydrochloric acid (HCl) and barium hydroxide (Ba(OH)2)?
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What is the chemical equation for the reaction between hydrochloric acid (HCl) and magnesium (Mg)?
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What is the chemical equation for the reaction between hydrochloric acid (HCl) and zinc carbonate (ZnCO3)?
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Write an equation in words to summarize the reaction of an alkali solution with dilute acids.
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Write an equation in words to summarize the reaction of an alkali solution with ammonium salts.
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Write an equation in words to summarize the reaction of an alkali solution with metal ions.
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Alkalis react with acids to produce ______ and ______.
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When a mixture of alkali and ammonium salt is heated, ______ gas is released.
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Addition of an alkali to most metal ions produces an ______ metal hydroxide precipitate.
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What is a standard solution?
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How is the concentration of a solution measured?
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What is the molarity of a solution that contains 10 moles of solute in 5 dm3 of solution?
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Concentration (g dm–3) = Mass of solute (g) ÷ Volume of solution (dm3)
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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?
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The reaction between HCl(aq) and Ba(OH)2(aq) results in the formation of _____.
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The reaction between H2SO4(aq) and KOH(aq) produces _____.
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The equation for the reaction between HNO3(aq) and NaOH(aq) is _____.
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Which of the following is true regarding the applications of neutralization?
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What are some nutrients that need to be replaced in soil for crop growth?
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What is urea produced from?
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What is the role of water in showing acidic and alkaline properties?
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What is the pH value related to?
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Acids produce _____ ions when dissolved in water.
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What defines a monoprotic acid?
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What happens when hydrogen chloride gas is dissolved in water?
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What are alkalis?
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All bases are alkalis.
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What is formed when an acid reacts with a base?
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Which of the following is an example of a diprotic acid?
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What is a standard solution?
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What do stalactites and stalagmites form from?
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The chemical formula for sodium hydroxide is _____?
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What is the aim of Activity 6.7?
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What materials are needed for preparing the standard solution?
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What is the first step in the procedure for preparing the solution?
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Why must the beaker and filter funnel be rinsed with distilled water?
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What is the significance of aligning the meniscus level with the calibration mark?
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Why does the volumetric flask need to be closed after preparation of the standard solution?
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What happens when sodium carbonate, Na2CO3 is dissolved in distilled water?
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What formula is used to calculate the molarity during dilution?
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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?
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Sodium hydroxide, NaOH, is suitable for preparing a standard solution.
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What is defined as neutralisation in chemistry?
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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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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.
