Chemistry MCQs

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Bananas contain potassium-40, a radioactive isotope of potassium, which makes them slightly radioactive. The radiation is very minor and not dangerous at all to humans, but it is enough to trigger sensitive radiation sensors. The potassium provides bananas some of their nutritional benefits as well.

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Alkali metals have one electron in their valence shell and hence they easily lose or donate electron.

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Hard water is generally found in areas where groundwater is in contact with limestone, chalk and dolomite and gets higher amount of calcium and magnesium dissolved in it.

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The auto-ignition temperature of a liquid, gas or vapor is the temperature at which the substance will ignite without any external heat source. Here is the temperature of some gases: 
Methane -580 °C 
Hydrogen -560 °C 
Propane -493 °C 
Ethylene -425 °C 
Acetylene -305 °C 
Naphtha -290 °C 
Carbon disulfide -102 °C

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Silica is also known as Silicon dioxide, is the most prevalent form of naturally occurring silicon.

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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.

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Francium is highly radioactive. its longest-lived isotope ²²³Fr has a half-life of only 21 minutes.

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An alloy is a homogeneous mixture of two or more metals, or a metal and a nonmetal. Alloying helps in improving the properties of a metal. The melting point of an alloy is less than that of pure metals.

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Calcination is the process of converting an ore into its oxide by heating it in a limited supply of air or in absence of air, below its melting point. It is used to convert the concentrated ore to its oxide.

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The Period in the modern periodic table indicates the value of ‘n’ (principal quantum number) for the outermost or valence shell.