Chemistry — Part 1 MCQs with Explanations

The Greenhouse effect is the main thing that causes global warming. It's like a blanket around the Earth. Certain gases in the atmosphere (like carbon dioxide) trap heat from the sun. Normally, some of this heat would escape back into space. But, when we burn too much fuel (like coal, oil, and gas), we release more of these gases. This makes the "blanket" thicker, trapping more heat and warming the planet. Let's look at why the other options are wrong: B) Fire in coal mines: While coal mine fires are bad for the environment, they don't cause global warming directly on a global scale like the greenhouse effect. C) Dry farming: Dry farming is a method of farming in dry areas. It can have environmental impacts, but it's not a direct cause of global warming . D) Monsoon: Monsoon are seasonal winds and rain. They are part of the Earth's climate system, but they don't cause global warming itself. In fact, climate change and global warming can affect monsoon patterns . E) Trade winds: Trade winds are constant winds in the tropics. Like monsoon, they are part of Earth's climate, not a cause of global warming . So, the greenhouse effect is the most important thing to understand when talking about global warming !

The nucleus of an atom consists of protons and neutrons.

Molality is the property of a a solution that is defined as the number of moles of solute per kilogram of solvent.

Fluorine is the most electronegative element and also the most reactive non-metal.

The metal used to recover copper from a solution of copper sulphate is Fe.

The number of d-electrons in Fe 2+ (Z=26) is not equal to the number of p - electrons in Cl(Z=17).

The process of extraction of metal in its molten state by any reducing agent in the presence of flux is called smelting.

Among the given gases, hydrogen at −50 o C has maximum value of T/M and highest speed.

The oldest rocks in the earth's crust were once molten, and came from deep inside the earth. The molten rock, called magma, spewed out in volcanic eruptions during the earth's early life and solidified into hard rock's called igneous rocks.

In physical chemistry, Henry's law is a gas law that states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid. The proportionality factor is called Henry's law constant.

Bicarbonate buffer is the most important buffer system in blood plasma (generally in the extracellular fluid). This buffer consists of weak acid H 2 CO 3 (pK1 = 6,1) and conjugated base HCO 3 - (bicarbonate).

Although ozone (O3) is present in small concentrations throughout the atmosphere, most ozone (about 90%) exists in the stratosphere, in a layer between 10 and 50 km above the surface of the earth. This ozone layer performs the essential task of filtering out most of the sun's biologically harmful UV radiation.

Bleaching agents are substances used to whiten or remove color. Option A: Alcohol - Alcohol is a good solvent and disinfectant, but it doesn't effectively remove color. Option B: Carbon Dioxide - Carbon dioxide is a gas we breathe out and is used in fire extinguishers and to make fizzy drinks. It doesn't have bleaching properties. Option C: Chlorine - Chlorine is widely used as a bleaching agent because it's very effective at breaking down the chemical compounds that cause color. Think of cleaning products and swimming pools – chlorine is often used in those. Option D: Sodium Chloride - Sodium chloride is actually common table salt (NaCl). It's important for our bodies but not a bleaching agent. Therefore, chlorine is the most common and effective bleaching agent among the options provided.

Most hydrogen atoms have nuclei that consist of a single proton, but a small fraction (about 0.015 percent) of the hydrogen atoms that occur in Nature have one neutron in addition to the proton in their nuclei.

The heat required to raise the temperature of a body by 1 K is called thermal capacity. In other words, when q is the heat supplied to the body and the temperature raises by 1 K, then the thermal capacity of body is q.

Nuclear particles responsible for holding all nucleons together are mesons. To account for the binding forces between like particles such as proton and proton or neutron and neutron, Kemmer suggested the existence of a neutral meson (π0).

Balanced chemical equation: P 4 + 5O 2 --------> P 4 O 10 1 mol 5 mol 1 mol 124g 160g 284g Here limiting reagent is P 4 . So, 124g of P 4 produce P 4 O 10 = 284g Therefore, 1.33g of P 4 produce P 4 O 10 = (284/124)*1.33 = 3.05g

n-heptane is defined as the zero point of the octane rating scale. 2,2,4-Trimethylpentane has an octane rating of 100, whereas n-heptane has an octane rating of 0. The octane number is based on an arbitrary scale which is a measure of its ability to resist knocking, as it burns on combustion.

Although nickel is the preferred catalyst for hydrogenation of fats and oils, the use of other metals such as palladium, platinum, ruthenium, and rhodium leads to products with less trans compounds.

The most abundant rare gas in the atmosphere is Argon (Ar).

The Latin word formica means ant. The name formic acid is derived from this Latin word because this acid was first obtained by the distillation of ants.

The ore which is found in abundance in India is monazite.

The inherited traits of an organism are controlled by DNA molecules. The traits an organism displays are ultimately determined by the genes it inherited from its parents, in other words by its genotype. Animals have two copies of all their chromosomes, one from each parent.

The heat energy produced when the human body metabolises 1 gram of fat is 39 KJ.

One mole of CO 2 has mass of 44 g and 32 g of O 2 . So 16 g of O 2 have 22 g of CO 2 or 0.5 moles of it.

The main use of salt in the diet is to produce in small amounts the hydrochloric acid required for the digestion of food.

Polyethylene is the most common plastic. The monomer is ethylene, a gaseous hydrocarbon with the formula C 2 H 4 which can be viewed as a pair of methylene groups connected to each other.

Metallic lustre is due to the mobile electrons present in metals which when de-excites releases energy in the form of light.

The number of water molecules present in a drop of water (volume 0.0018 ml) at room temperature is 6.023 x 10 19 .

The most malleable metal is gold.

The oil used in froth flotation process in pine oil, it is because it does not have affinity towards water and it easily attracts impurities and impurities can easily wash away.

The number of waves in n x 10 th Bohr's orbit are n waves.

The mass of one Avogadro number of helium atom is 4 x 6.02 x 10 23 gram.

The items amenable to detection by soft x-rays are genuine coins from counterfeit coins.

The material which can be deformed permanently by heat and pressure is called thermoset.

The mass number (A), is the total number of protons and neutrons ns) in an atomic nucleus so sometimes more than and sometimes equal to its atomic number, depends upon no of neutrons.

The inexpensive and commonly used variety of glass is called soda glass. It is called so because is made using soda(sodium carbonate).

Hydrogenation - to treat with hydrogen - is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. The largest scale application of hydrogenation is for the processing of vegetable oils (fats to give margarine and related spreads and shortenings). Typical vegetable oils are derived from polyunsaturated fatty acids (containing more than one carbon-carbon double bonds). Their partial hydrogenation reduces most but not all, of these carbon-carbon double bonds. Hydrogenation converts liquid vegetable oils into solid or semi-solid fats, such as those present in margarine.

The ionic radii of N 3- , O 2- , F - and Na + follows the order N 3- > O 2- > F - > Na +

In nuclear reactor graphite rods are used as moderator or controller. Application of moderator is to slow down the neutron and controller is to control the number of neutron.