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Questions and Answers
A scientist is testing an unknown solution. They observe that it turns blue litmus paper red. Based on this observation, which of the following is most likely true?
A scientist is testing an unknown solution. They observe that it turns blue litmus paper red. Based on this observation, which of the following is most likely true?
- The solution has a pH less than 7 and will react with metal carbonates to produce carbon dioxide. (correct)
- The solution is neutral and will not react with either acids or bases.
- The solution has a pH greater than 7 and contains excess hydroxyl ions.
- The solution is a base and will react with a metal to produce hydrogen gas.
Which of the following correctly matches a natural source with its corresponding acid?
Which of the following correctly matches a natural source with its corresponding acid?
- Vinegar - Citric acid
- Tamarind - Tartaric acid (correct)
- Orange - Acetic acid
- Lemon - Tartaric acid
Vanilla extract is tested with both hydrochloric acid (HCl) and sodium hydroxide (NaOH). What change would indicate that vanilla extract functions as an olfactory indicator?
Vanilla extract is tested with both hydrochloric acid (HCl) and sodium hydroxide (NaOH). What change would indicate that vanilla extract functions as an olfactory indicator?
- The vanilla extract exhibits a change in odor in both the HCl and NaOH solutions. (correct)
- The vanilla extract changes color only in the NaOH solution.
- The vanilla extract changes color only in the HCl solution.
- The vanilla extract shows no change in either solution.
In a chemical reaction, a student mixes an unknown substance with both an acid and a base. The substance turns red in the acid and remains yellow in the base. Based on the reference table, what substance could this be?
In a chemical reaction, a student mixes an unknown substance with both an acid and a base. The substance turns red in the acid and remains yellow in the base. Based on the reference table, what substance could this be?
A solution has a pH of 2. Which statement accurately describes how dilution with water affects this solution?
A solution has a pH of 2. Which statement accurately describes how dilution with water affects this solution?
A gardener notices that the soil in their garden is too alkaline for the plants they want to grow. Which action would best help adjust the soil pH to a more suitable level?
A gardener notices that the soil in their garden is too alkaline for the plants they want to grow. Which action would best help adjust the soil pH to a more suitable level?
During a lab experiment, hydrochloric acid (HCl) is mixed with zinc (Zn). Which observation would confirm that a chemical reaction has taken place?
During a lab experiment, hydrochloric acid (HCl) is mixed with zinc (Zn). Which observation would confirm that a chemical reaction has taken place?
Carbon dioxide ($CO_2$) is bubbled through lime water ($Ca(OH)_2$). What observation indicates the acidic nature of the non-metal oxide?
Carbon dioxide ($CO_2$) is bubbled through lime water ($Ca(OH)_2$). What observation indicates the acidic nature of the non-metal oxide?
A student wants to determine the strength of several acid solutions. Which tool would provide the most accurate measurement for comparing the concentration of hydrogen ions in these solutions?
A student wants to determine the strength of several acid solutions. Which tool would provide the most accurate measurement for comparing the concentration of hydrogen ions in these solutions?
Which of the following describes the industrial process where sodium hydroxide ($NaOH$) is produced alongside chlorine gas ($Cl_2$) and hydrogen gas ($H_2$)?
Which of the following describes the industrial process where sodium hydroxide ($NaOH$) is produced alongside chlorine gas ($Cl_2$) and hydrogen gas ($H_2$)?
In the chlor-alkali process, what is the purpose of the membrane separating the anode and cathode?
In the chlor-alkali process, what is the purpose of the membrane separating the anode and cathode?
Which of the following is a use of Hydrogen gas produced during the chlor-alkali process?
Which of the following is a use of Hydrogen gas produced during the chlor-alkali process?
During the production of $NaHCO_3$, what are the necessary reactants?
During the production of $NaHCO_3$, what are the necessary reactants?
Why is sodium hydrogen carbonate ($NaHCO_3$) used in soda-acid fire extinguishers?
Why is sodium hydrogen carbonate ($NaHCO_3$) used in soda-acid fire extinguishers?
A student adds hydrochloric acid ($HCl$) to copper(II) oxide ($CuO$). What observation confirms the formation of copper(II) chloride ($CuCl_2$)?
A student adds hydrochloric acid ($HCl$) to copper(II) oxide ($CuO$). What observation confirms the formation of copper(II) chloride ($CuCl_2$)?
Flashcards
Acid
Acid
Sour taste, turns blue litmus paper red, pH < 7, releases H+ ions in solution.
Base
Base
Bitter taste, soapy feel, turns red litmus paper blue, pH > 7, releases OH- ions.
Indicators
Indicators
Change color in the presence of an acid or a base.
Olfactory Indicators
Olfactory Indicators
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Strong Acids & Bases
Strong Acids & Bases
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Diluted Acid
Diluted Acid
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Soil pH for Plants
Soil pH for Plants
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Litmus Solution
Litmus Solution
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Acid + Metal Reaction
Acid + Metal Reaction
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pH Definition
pH Definition
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Salt
Salt
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Sodium Chloride (NaCl)
Sodium Chloride (NaCl)
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Chlor-Alkali Process
Chlor-Alkali Process
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Sodium Bicarbonate uses
Sodium Bicarbonate uses
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Carbon Dioxide
Carbon Dioxide
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Study Notes
- Acids taste sour and turn blue litmus paper red
- Acids give hydrogen ions in solutions with a pH less than 7
- Example acids: Hydrochloric Acid (HCl), Acetic Acid (CH3COOH)
- Bases taste bitter and feel soapy, turning red litmus paper blue
- Bases give hydroxyl ions in solutions with a pH greater than 7
- Example base: Sodium Hydroxide (NaOH)
Natural Sources of Acids
- Vinegar contains Acetic acid
- Oranges and Lemons contain Citric acid
- Tamarind contains Tartaric acid
- Tomatoes contain Oxalic acid
- Sour milk (Curd) contains Lactic acid
- Ant and Nettle stings contain Methanoic acid
Indicators
- Indicators are chemical compounds that change color depending on whether they're in an acidic or basic environment
- Olfactory indicators change their odor in acidic or basic mediums, examples include Vanilla, Onion, clove oil
- In a base olfactory indicators have no smell and in an acid the smell remains
- Litmus (natural) has a pale purple color in neutral solutions, turns red in acid, and blue in base
- Hydrangea flowers (natural) are blue in neutral solutions, blue in acid and pink in base
- Turmeric (natural) is yellow in neutral and acidic solutions, and red in base
- Phenolphthalein (synthetic) is colorless in acid, and pink in base
- Methyl Orange (synthetic) is red in acid and yellow in base
Acids, Bases, and Ion Concentration
- Strong acids release more hydrogen ions (H+), while weak acids release fewer
- The same applies to bases
- Dilution reduces the concentration of H3O+ or OH- ions per unit volume by mixing an acid or base with water
- Diluted acid has a small amount of acid (solute) in a large amount of water (solvent)
- Concentrated acid has a large amount of acid in a small amount of water.
Chemical properties of acids
- Acids and Metals produce Salt and Hydrogen gas, for example: Zn + 2HCl → ZnCl2 + H2
- Bubbles in soap solution may ignite near a burning candle
- Acids and Metal Carbonates produce 2NaCl + CO2 + H2O, for example: Na2CO3 + 2HCl →
- The Carbon dioxide turns lime water milky, indicating its presence
- Acids and Metal Hydrogencarbonates produce NaCl + CO2 + H2O eg: NaHCO3 + HCl →
- Acids and Metallic Oxides produce a salt and water eg: CuO + 2HCl → CuCl2 + H2O
- The solution turns blue-green, indicating the formation of copper(II) chloride
Acids/Bases - pH scale
- A universal indicator estimates acid and base strength
- Universal indicators show different colors at different concentrations of H+ ions
- pH measures the concentration of hydrogen ions (power of hydrogen)
- pH less than 7 is Acidic
- pH equal to 7 is Neutral
- pH greater than 7 is Basic
- Strong acid with strong base results in neutral pH 7
- Strong acid with weak base results in acidic pH < 7
- Strong base with weak acid results in basic pH > 7
Examples of Neutralization
- Base + Acid produces Salt + Water
- NaOH + HCl → NaCl + H2O
- Sodium Chloride (NaCl) is neutral
Sodium Chloride (NaCl)
- Formed from HCl + NaOH
- Found in seawater and rock salt deposits
- Used in food seasoning and as a raw material for chemicals like NaOH
Sodium Hydroxide (NaOH)
- Produced by electrolysis of brine (Chlor-alkali process)
- At anode, Chlorine gas (Cl2) is produced which is used in water treatment, for PVC, and disinfectants
- At cathode, Hydrogen gas (H2) is produced, which is used for fuels and margarine
- Near cathode, Sodium Hydroxide (NaOH) solution is produced, which is used in soap, paper, and textiles
Sodium Hydrogen Carbonate (NaHCO3)
- Produced using sodium chloride, water, and carbon dioxide: NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3
- Used in baking powder, antacids, and soda-acid fire extinguishers
Importance of pH in daily life
- Digestion: The stomach uses hydrochloric acid with a pH of 1 to 3 to break down food
- Soil: Plants grow best in soil with a pH of 6.3 to 7.3
- Add lime to soil if it is too acidic and gypsum if it is too basic
- Tooth Decay: Bacteria in the mouth make it acidic, leading to tooth decay
- Toothpaste balances the mouth's pH
- Blood: Functions best with a pH between 7.0 to 7.8
- Plants and Animals: They prefer specific pH levels
- Most plants grow best in soil around pH 7
- Bee Stings: Baking soda neutralizes the acidity caused by bee stings
- Acid Rain: Pollution makes rain acidic and harms fish and other animals
Salts
- Salts are ionic compounds composed of positively charged ions (cations) and negatively charged ions (anions)
- These ions are held together by ionic bonds
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Description
Acids, bases, and indicators are fundamental concepts in chemistry. Acids taste sour and turn blue litmus paper red, while bases taste bitter and turn red litmus paper blue. Indicators are substances that change color depending on the pH of the solution.
