and oxygen and the carbon in it weighs 6 grams, what will be the weight of the oxygen ? The atomic hypothesis is subject to doubt and controversy because recent observations suggest atoms are not indivisible. However, even if atoms prove divisible into smaller particles ('electrons'), the facts supporting the atomic theory remain unchanged, and Avogadro's law remains intact. New discoveries may refine but not destroy this foundational concept.
- How much sulphur can be held in combination by 50 grams of mercury ?
- How much chlorine can be held in combination by 27.5 grams of manganese ?
- How much chlorine can be held in combination by 7 grams of nitrogen ?
- If a mass of 108 grams of a compound of mercury and oxygen is decomposed, how much will the mercury weigh and how much will the oxygen weigh ?
- Formulate Dalton's laws concerning chemical combining proportions.
- What is the atomic theory ? It explains that elements combine in simple whole number ratios to form compounds.
- How does it explain the law of multiple proportions ? By stating that when two elements form more than one compound, their masses are in a ratio of small whole numbers.
- What is the molecular weight of any substance? The sum of atomic weights of atoms in its molecule.
- What would you call the minimum relative mass of an element capable of chemical combination with others ? Its atomic weight.
- If chlorine's atomic weight is 35.5, what is its molecular weight if diatomic ? 71 grams per mole.
- What if molecules are monatomic? 35.5 grams per mole.
- If mercury's vapor density is 200, assuming the molecule contains half as many atoms as hydrogen, what is its atomic weight? 200 grams per mole.
- What is Avogadro's law ? Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
- Is the smallest individual particle of matter necessarily a molecule? No, it could be an atom or ion.
- If vapor density doubles from 500° to 1000° for any gas, what does this indicate ? It suggests molecular volume changes with temperature.
- If heating a certain gas to 2000° causes its volume to double, how do you explain that? The gas molecules expand due to increased thermal energy.
- Can any gas increase in volume by rising temperature without molecule division? Yes, but expansion rate depends on molecular structure and intermolecular forces.
- State Gay-Lussac's proposition. Equal volumes of gases at the same conditions contain equal numbers of molecules.
- If 3 liters of oxygen combine with 6 liters of hydrogen, what compound forms and how much? Water vapor (H2O), forming 3 liters of H2O vapor.
- State Dulong and Petit's law. The specific heat capacity of a solid element is inversely proportional to its atomic weight.
- Define specific heat. Heat required to raise the temperature of one gram of substance by one degree Celsius.
- If you divide an element’s atomic weight by 6.4, what does the quotient represent? Its approximate specific heat capacity.
- How can molecular weight be verified by specific heat? By comparing calculated and measured specific heats.
- How can vapor density verify molecular weight? By using Avogadro's law to relate volume to number of molecules.
VIII Chemical Polarity 147. Positive and Negative Elements. Metals and hydrogen behave similarly in chemical reactions, taking each other’s places without changing their nature. No metal forms a true compound with hydrogen directly; non-metals do form such compounds with hydrogen. Water decomposes under electric current, collecting hydrogen at the negative pole and oxygen at the positive pole.
Chemical Polarity refers to opposite qualities of elements combining directly. Only opposites combine.
Fluorine, chlorine, bromine, iodine have a greater affinity for hydrogen than oxygen. Chlorine does not form oxides; others do but are unstable salts.
Certain compounds in solution dissociate into ions under electric current. Positive ions (kations) collect at the negative electrode (katode), and negative ions (anions) at the positive electrode (anode). Water decomposes with hydrogen at the negative pole and oxygen at the positive pole when an electrolyte like sulfuric acid is added.
Omitting elements that do not form compounds, and those invariably positive or negative, thirteen non-metallic elements remain capable of varying polarity. Their valence can be partly positive or negative depending on combinations with other elements.
Test Questions 1-14 cover identifying polarities in various compounds and understanding binary compound structures.
IX Binary Compounds 152. A binary compound consists of two elements, one positive and the other negative, united such that each atom is directly combined with an atom of the opposite element. Examples include sodium chloride (NaCl), calcium oxide (CaO), hydrogen chloride (HCl).
<Callout type="important" title="Key Concept: Binary Compounds">Binary compounds are fundamental in understanding molecular structure and chemical reactions.</Callout>
Names of binary compounds end with “-ide,” derived from their negative elements.
True binary compounds fall into fifteen classes based on their negative elements, including fluorides, oxides, chlorides, bromides, iodides, etc.
<Callout type="tip" title="Quick Tip: Naming Compounds">Remember to use the suffix “-ide” for naming binary compounds.</Callout>
- Halides (fluorides, chlorides, bromides, iodides) never contain more than one atom of the element directly united with a negative halogen.
<Callout type="warning" title="Safety Alert: Handling Compounds">Be cautious when handling compounds like hydrogen dioxide; they may not be true binary compounds and can be hazardous.</Callout>
Key Takeaways
- Understanding chemical polarity helps in predicting how elements combine.
- Binary compounds are fundamental to understanding molecular structures and reactions.
- The atomic hypothesis remains foundational despite recent discoveries.
Practical Tips
- Use the suffix “-ide” when naming binary compounds based on their negative element.
- Be aware of Avogadro's law in calculating molecular weights from vapor densities.
Warnings & Risks
- Handle hydrogen dioxide with caution as it may not be a true binary compound and can pose risks.
- Electrolysis requires careful handling due to potential hazards associated with ion separation.
Modern Application
While the chapter focuses on historical chemical theories, understanding these principles remains crucial for modern survival scenarios. Knowledge of molecular structures and reactions is vital in fields like emergency medicine (for compound identification) and environmental science (for pollutant analysis).
Frequently Asked Questions
Q: What are binary compounds?
Binary compounds consist of two elements, one positive and the other negative, united such that each atom is directly combined with an atom of the opposite element.
Q: How do you identify chemical polarity in a compound?
Chemical polarity can be identified by understanding the valence and combining behavior of elements. For example, metals are positive while non-metals like oxygen are negative.
Q: What is Avogadro's law?
Avogadro's law states that equal volumes of gases at the same temperature and pressure contain an equal number of molecules.