Question

Elements number 17 and 20 form compounds with hydrogen. Write the formulas for these two compounds, and compare their chemical behavior in water.

Short answer

HCl forms an acidic solution in water, while CaH2 forms a basic one.

Step-by-step solution

Identify Elements 17 and 20

Element number 17 is Chlorine (Cl), and element number 20 is Calcium (Ca) in the periodic table. These elements can form compounds with hydrogen.

Determine Compounds with Hydrogen

Chlorine forms a compound with hydrogen called Hydrogen Chloride (HCl) and Calcium forms a compound called Calcium Hydride (CaH2). Thus, the formulas for these compounds are HCl and CaH2 respectively.

Describe HCl Behavior in Water

Hydrogen Chloride (HCl) dissolves in water to form hydrochloric acid (HCl), which is a strong acid. It dissociates completely in water into H⁺ and Cl⁻ ions, resulting in an acidic solution.

Describe CaH2 Behavior in Water

Calcium Hydride (CaH2) reacts with water in a chemical reaction to produce calcium hydroxide ( Ca(OH)2 ) and hydrogen gas ( H2 ). The reaction produces a solution that is basic due to the formation of calcium hydroxide, a strong base.

Compare Chemical Behavior

In water, HCl exhibits acidic behavior due to complete dissociation, whereas CaH2 shows basic behavior as it forms calcium hydroxide. Therefore, their chemical reactions with water result in solutions with opposite pH levels: acidic for HCl and basic for CaH2.

Key concepts

Hydrogen Compounds

Hydrogen is a unique element that forms compounds with many other elements across the periodic table. When hydrogen connects with other elements, it creates hydrogen compounds such as hydrogen chloride (HCl) and calcium hydride (CaH\(_2\)). These compounds have diverse chemical properties and behaviors, especially noticeable when they interact with water.
HCl, for instance, readily dissolves in water, producing hydrochloric acid, a strong acid. It releases hydrogen (H\(^+\)) ions very easily, making the solution more acidic. On the other hand, calcium hydride (CaH\(_2\)) reacts with water to form calcium hydroxide and hydrogen gas, resulting in a basic solution due to the hydroxide ions produced.
Understanding these hydrogen compounds helps in predicting their chemical behavior and how they affect solutions when mixed with water.

Periodic Table Elements

The periodic table is an organized chart of chemical elements, arranged by increasing atomic number. It helps to predict element properties and behaviors. Element 17 is Chlorine (Cl), a non-metal found in the halogens group, known for forming salts. Meanwhile, element 20 is Calcium (Ca), an alkaline earth metal, often found in minerals and bones.
Although Chlorine and Calcium belong to different families, they both form significant hydrogen compounds. Chlorine, when combined with hydrogen, forms hydrogen chloride (HCl). This is a gas at room temperature and dissolves in water to form acidic solutions. Calcium combines to create calcium hydride (CaH\(_2\)), often helping to generate basic conditions when reacting with water.

• Chlorine (Cl): Non-metal, halogen group, forms acidic compounds with hydrogen.
• Calcium (Ca): Metal, alkaline earth group, forms basic compounds with hydrogen.

Recognizing these elements in the periodic table allows better understanding of their chemical interactions.

Acidic and Basic Solutions

Solutions can be acidic or basic based on the types and concentrations of ions they release in water. Acidic solutions contain a high concentration of hydrogen ions (H\(^+\)), whereas basic solutions have more hydroxide ions (OH\(^-\)). The pH scale measures how acidic or basic a solution is, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral.
Hydrogen chloride (HCl) forms hydrochloric acid when dissolved in water. It completely dissociates into hydrogen and chloride ions, resulting in a low pH, making the solution acidic. This complete dissociation explains why hydrochloric acid is a strong acid. Conversely, calcium hydride (CaH\(_2\)) reacts with water to form calcium hydroxide. The result is a solution rich in hydroxide ions, which means it has a high pH, indicating a basic solution.
Understanding the balance and effects of ions in a solution helps in determining whether it is acidic or basic, which is crucial for various chemical processes.