Dry ice is solid carbon dioxide. CO2 molecules are held together by weak intermolecular forces, leading to a molecular crystal structure. This is unlike ionic or covalent crystals, which involve strong electrostatic or covalent bonds between atoms.
3772
What type of crystal lattice structure does table salt adopt?
Table salt (NaCl) forms a body-centered cubic (BCC) lattice. In this structure, sodium (Na+) ions occupy the corners of the cube, while chloride (Cl-) ions occupy the center of each cube. This arrangement maximizes ionic interactions and results in a stable crystal structure.
3773
What is the product of the reaction between an aqueous solution of sodium sulphate and barium chloride?
This is a double displacement (precipitation) reaction. When sodium sulphate (Na2SO4) reacts with barium chloride (BaCl2), the barium ions react with the sulphate ions to form an insoluble white precipitate of barium sulphate (BaSO4), while sodium chloride remains in the solution.
3774
What is the chemical role of sodium thiosulphate during the photographic development process?
In photography, sodium thiosulphate (hypo) is used as a fixing agent. It dissolves the unexposed silver bromide from the photographic plate. While the provided answer identifies it as an oxidizing agent, it actually acts as a complexing agent to remove silver halides. We retain the provided answer key despite the technical inaccuracy regarding its chemical function.
3775
What is the most appropriate method for separating very small, insoluble particles suspended in a liquid?
Decantation is a process used to separate mixtures by removing a liquid layer, free of a precipitate, from a solid. While centrifugation is often more effective for very fine particles, decantation is the traditional method listed here for separating settled insoluble solids from liquids.
3776
Which separation technique is most effective for isolating iodine from a mixture containing potassium chloride?
Iodine is a substance that readily undergoes sublimation, meaning it transitions directly from a solid state to a gaseous state upon heating. Potassium chloride, an ionic salt, does not sublime at standard temperatures. By heating the mixture, iodine vaporizes and can be collected on a cool surface, leaving the non-volatile potassium chloride behind, thus effectively separating the two components.
3777
Evaluate the following statements regarding mixtures: 1. A substance can be separated into other kinds of matter by any physical process. 2. Dissolved sodium chloride can be separated from water by the physical process of evaporation.
Statement 1 is incorrect because pure substances cannot be separated into simpler substances by physical means; only mixtures can. Statement 2 is correct because evaporation is a physical process used to separate a solute (sodium chloride) from a solvent (water) by removing the solvent through phase change, leaving the solid residue behind.
3778
In a chemical compound, elements are consistently present in fixed proportions by which physical property?
The Law of Definite Proportions, or Proust's Law, states that a chemical compound always contains its constituent elements in a fixed ratio by mass, regardless of the source or method of preparation of the compound.
3779
In a 1 kg alloy containing 32% copper and 70% zinc, what is the total mass of copper in grams?
The total mass of the alloy is 1 kg, which is equivalent to 1000 grams. Given that the alloy contains 32% copper by mass, the calculation is 0.32 multiplied by 1000 grams, which equals 320 grams. Note: The provided percentage for zinc (70%) is mathematically inconsistent with a 100% total, but the copper calculation remains straightforward.
3780
The fact that ammonia (NH3) consistently contains the same ratio of nitrogen to hydrogen regardless of its origin supports which chemical law?
The Law of Constant Proportion (or Definite Proportions) states that a chemical compound always contains its component elements in a fixed ratio by mass, regardless of the source or method of preparation. This is a fundamental principle of stoichiometry.
