Lesson 5: Acids, Bases, Peat Bogs, and pH Scale

Comprehensive practice flashcards covering Lesson 5 on acids, bases, peat bogs, bog bodies, indicator tests, metal and carbonate reactions, and the pH scale.

What is peat?

A brown deposit resembling soil, formed by the partial decomposition of vegetable matter in the wet acidic conditions of bogs and fens, and often cut out and dried for use as fuel and in gardening.

What is a bog or bogland?

A wetland that accumulates peat as a deposit of dead plant materials, which are often mosses.

What are bog bodies, and why are they so well-preserved?

Bog bodies are ancient human remains found in peat bogs dating back thousands of years. They are well-preserved due to the acidic and anaerobic (low-oxygen) conditions of the bog.

Why are peat bogs ecologically important?

Peat bogs help regulate the Earth's climate by storing carbon dioxide, provide habitats for many rare species (including birds and insects), and assist in water filtration and flood control.

Where do peat bogs typically develop, and under what conditions does peat form?

Peat bogs are found worldwide, especially in temperate and boreal regions, developing in glacial landscapes, low-lying areas, and other wetlands. Peat forms slowly under wet, acidic, and anaerobic conditions as dead plant matter accumulates over time.

What is an acid and what are its general chemical properties?

An acid is a chemical substance containing hydrogen that tastes sour, stings or burns skin, conducts electricity in solution, has a $pH < 7.0$, turns blue litmus paper red, releases or donates $H^+$ ions in water, reacts with active metals to produce $H_2$ gas, and reacts with bases to form water and a salt.

How do litmus paper, phenolphthalein, and methyl orange respond to acids versus bases?

In acids, litmus is red, phenolphthalein is colorless, and methyl orange is red. In bases, litmus is blue, phenolphthalein is pink, and methyl orange is yellow.

What specific natural acids are found in lemons, red ants, yogurt, tomatoes, tamarind, and vinegar?

Lemons contain citric acid; red ants contain formic acid; yogurt contains lactic acid; tomatoes contain citric acid (primary) and malic acid; tamarind contains tartaric acid; and vinegar contains acetic acid.

What are the observed effects of acid deposition on red spruce and sugar maple trees?

On red spruce, calcium is leached from needle membranes, leading to decreased cold tolerance and increased freezing injury. On sugar maple, calcium and magnesium are leached from the soil while aluminum is mobilized and taken up by the tree.

Based on the molecular behavior shown in the diagram, what distinguishes a strong acid from a weak acid in aqueous solution?

Strong acids completely dissociate or ionise when dissolved in water, resulting in a lower $pH$. Weak acids only partially dissociate or ionise, leaving undissociated molecules in water and resulting in a higher $pH$.

Which acids are classified in the lecture notes as strong acids and weak acids?

Strong acids include hydrochloric acid ($HCl$), nitric acid ($HNO_3$), hydroiodic acid ($HI$), perchloric acid ($HClO_4$), and chloric acid ($HClO_3$). Weak acids include sulfurous acid ($H_2SO_3$), methanoic acid ($HCO_2H$), phosphoric acid ($H_3PO_4$), nitrous acid ($HNO_2$), and hydrofluoric acid ($HF$).

What general products are formed when an acid reacts with an active metal?

An acid reacts with an active metal to produce a salt and hydrogen gas ($\text{metal} + \text{acid} \rightarrow \text{salt} + \text{hydrogen}$), such as hydrochloric acid reacting with zinc to form zinc chloride and hydrogen.

Why do noble metals like gold and platinum resist corrosion and not react with acids?

Noble metals have a strong atomic structure with tightly held electrons, making it difficult for acids to break them apart.

What testing method is demonstrated in this image, and how does it determine gold quality?

Testing gold purity with a touchstone; gold is rubbed on the stone to produce a mark, acid is applied, and the resulting streak is compared to known standards.

What does the $pH$ scale measure, and what is the linguistic origin of the letter 'p'?

The $pH$ scale measures the concentration of hydrogen ions ($H^+$) in solution on a scale from $0$ to $14$. The letter 'p' stands for 'potenz' in German, meaning power (or potential).

What is the primary operational difference between litmus paper and $pH$ paper?

Litmus paper only indicates whether a substance is acidic or basic without providing a numerical value, whereas $pH$ paper indicates the exact $pH$ value ($1-14$) through specific color changes for each level.

According to the test depicted in this diagram, how do blue and red litmus papers respond to acidic and basic solutions?

In an acid, blue litmus paper turns red; in a base, red litmus paper turns blue.

What products are produced when acids react with carbonate compounds?

Acids react with carbonates to produce carbon dioxide gas, water, and a salt ($\text{acid} + \text{carbonate} \rightarrow \text{carbon dioxide} + \text{water} + \text{salt}$).

What is the balanced equation for the reaction between acetic acid (vinegar) and baking soda (sodium hydrogen carbonate)?

$HC_2H_3O_2\,(aq) + NaHCO_3\,(aq) \rightarrow CO_2\,(g) + H_2O\,(l) + NaC_2H_3O_2\,(aq)$, producing carbon dioxide, water, and sodium acetate.

In the experimental apparatus shown, how is the gas produced from acid reacting with marble chips identified?

The gas produced is carbon dioxide ($CO_2$); when passed through a delivery tube into a limewater solution, it causes the limewater to turn milky.

According to the lecture $pH$ reference chart, what are the specific $pH$ values of lemon juice, wine, rain, human blood, baking soda, and bleach?

Lemon juice has a $pH$ of $2.0$, wine is $4.0$, rain is $5.5$, human blood is $7.5$, baking soda is $8.5$, detergent is $10.0$, and bleach has a $pH$ of $12.5$.

What are the essential safety rules for handling acids described in the lecture?

Always wear safety goggles and gloves when handling acids, and never mix acids with bases without supervision.