Chemistry MCQs

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John Dalton introduced the atomic theory into chemistry. The main points of Dalton’s atomic theory are (1) Elements are made of extremely small particles called atoms. (2) Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.(3) Atoms cannot be subdivided, created or destroyed. (4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. (5) In chemical reactions, atoms are combined, separated or rearranged.

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Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. When oxidation occurs, an element loses electrons and its oxidation number increases .i.e. it becomes more positive.

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When iron or any other metal oxidizes, oxygen from the air combines with the iron to make iron oxide or rust. So, weight of the bar increases, due to the increased weight of oxygen which has combined with the iron. over time, the weight of the iron bar will tend to decrease, due to factors related more to erosion than to chemistry.

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Platinum is a naturally white metal. It doses not need to be alloyed for color. Due to its appearance as white, it is commonly known as White Gold.

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Helium atoms that have lost two electrons are called alpha rays. Alpha rays are also called alpha particles or alpha radiation. Alpha particles are made up of two protons and two neutrons bound together into a particle that is identical to a helium-4 nucleus.
Alpha particles are named after the first letter in the Greek alphabet, α. They were the first nuclear radiation to be discovered.
When a helium atom loses its electrons, it is left with only the nucleus. This is called an alpha particle.

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Froth and foams are examples of “gas suspended in liquid”. They are typically created when gas bubbles are dispersed in a liquid. This physical phenomenon is commonly observed in many daily life scenarios such as soap lather and carbonated drinks. Technically, they are a special case of colloid where little blobs of one liquid are dispersed in another and show the property of surface tension.

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Chlorine has an atomic number of 17, meaning it has 17 protons. Its atomic weight is approximately 35, which indicates it typically has 18 neutrons (35 – 17 = 18). Therefore, the correct composition is 17 protons and 18 neutrons. Chlorine is a halogen and exists primarily as two stable isotopes: Chlorine-35 and Chlorine-37.

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When Mendeleev published his periodic table in 1869, noble gases had not yet been discovered. The first noble gas, argon, was identified in 1894 by Lord Rayleigh and William Ramsay. In contrast, lanthanides and actinides were recognized later, but their existence was inferred from Mendeleev’s predictions. Halogens, including elements like chlorine and iodine, were known prior to Mendeleev’s work.

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Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulphuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms.

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The alkaline earth metals have low ionization enthalpies due to fairly large size of the atoms. Since the atomic size increases down the group, their ionization enthalpy decreases.