Tag: science & technology

Isotopes are atoms of the same element that have identical atomic numbers (same number of protons) but different mass numbers (different numbers of neutrons). Isobars have different atomic numbers but same mass number. Isotones have same number of neutrons but different protons. Nuclear isomers are excited states of nuclei.

Dmitri Mendeleev created the first successful periodic table in 1869, arranging elements by atomic weight and leaving gaps for undiscovered elements. His predictions about missing elements proved correct. Lavoisier categorized elements but didn't create a periodic table. Newlands proposed the Law of Octaves. Kekulé is famous for work on organic chemistry structure, not periodic tables.

Aluminium is a trivalent impurity (3 valence electrons) while silicon is tetravalent (4 valence electrons). When aluminium atoms are added to silicon, they create electron deficiencies called 'holes' in the crystal structure, making it a p-type semiconductor where holes are the majority charge carriers. Aluminium acts as an acceptor impurity.

Bromine is the only non-metal that exists as a liquid at room temperature (25°C). It is a halogen in Group 17 with atomic number 35, appearing as a reddish-brown volatile liquid that readily evaporates to form a similarly colored gas. Mercury is a metal, while astatine and iodine are solids at room temperature.

ATP (Adenosine Triphosphate) is the primary energy currency of the cell. It consists of an adenine base, a ribose sugar, and three phosphate groups. When energy is needed, the terminal phosphate bond is broken to release energy, forming ADP (Adenosine Diphosphate). The other options are made-up terms.

Oxygenic photosynthesis uses water, carbon dioxide, and light energy to produce glucose and oxygen. The oxygen released comes from the splitting of water molecules during the light-dependent reactions, not from carbon dioxide. This process occurs in plants, algae, and cyanobacteria. Water is consumed, not produced; chlorophyll is a pigment that absorbs light, not a byproduct.

This is correct. The three primary factors determining blood alcohol content are: 1) body size/weight (larger bodies have more blood volume to dilute alcohol), 2) total amount of alcohol consumed, and 3) rate of drinking (faster drinking leads to higher peak BAC).

When sound travels to the cliff and reflects back as an echo, measuring the round-trip time allows distance calculation. Using the formula distance = (speed of sound × time) / 2, you can determine how far the cliff is.

The -CO- group (carbonyl group with carbon double-bonded to oxygen, flanked by two carbon atoms) is called a ketone. In organic chemistry, ketones are characterized by this R-CO-R' structure where carbon is bonded to two alkyl groups. Acids contain -COOH, esters have -COO-, and ethers have R-O-R structures, so the ketone identification is correct.

The -COOH functional group is called carboxylic acid, commonly shortened to 'acid'. This group consists of a carbonyl (C=O) and hydroxyl (-OH) bonded to the same carbon. Option A shows 'ASID' which is a typo for 'ACID', but it's clearly meant to be the correct answer. Esters contain -COO-, amides contain -CONH2, and amino groups contain -NH2.