General Science GK Questions with Answers – Page 67

Magnesium, calcium and barium are all alkaline earth metals of group 2, and each has a valency of 2. Elements in the same group of the periodic table have the same number of electrons in their outermost shell, and so the same valency.

Their valencies are neon 0, magnesium 2, nitrogen 3 and silicon 4. Valency is the combining capacity of an atom, the number of electrons it loses, gains or shares to reach a stable octet.

Electric power is P = V × I, and 220 V × 0.6 A = 132 W. Power is the rate at which electrical energy is used, measured in watts; one watt is one joule per second, or one volt times one ampere.

Mitochondria are membrane-bound organelles, and only eukaryotic cells have membrane-bound organelles. Prokaryotes such as bacteria and cyanobacteria have no true nucleus and no membrane-bound organelles; their DNA lies in a region called the nucleoid, and they carry out respiration on their plasma membrane.

Only this split of boron-10 and boron-11 gives an average atomic mass of 10.81. The relative atomic mass of an element is the average of its isotopes' masses, each weighted by how common it is.

Inside a long current-carrying solenoid the magnetic field has the same strength and direction at every point, shown by parallel, evenly spaced field lines.

A work done that is fixed by the starting and ending speeds alone is exactly what the work-energy theorem states: W(net) = ½mv² − ½mu².

The longer wire's resistance works out to 2.88 times that of the shorter one, which is 188% more. Resistance is R = ρL/A, where ρ is the resistivity of the material.

Of the three forms of carbon, only fullerenes are made of closed, hollow, cage-like molecules. The best-known fullerene is buckminsterfullerene, C60, a hollow sphere of 60 carbon atoms arranged in 20 hexagons and 12 pentagons, shaped like a football.

A simple periscope has two plane mirrors, and light reaches the eye only by bouncing off them. In a simple periscope, two plane mirrors are fixed parallel to each other at the two bends of a long tube, each tilted at 45° to its length.

A mixture of carbon monoxide and hydrogen is called synthesis gas, or syngas, because it is the starting material for making methanol and many other compounds.

This is sodium stearate, the sodium salt of a long-chain fatty acid, which makes it a soap and not a synthetic detergent.

This statement is false: water is a strongly polar molecule. In a water molecule the oxygen atom is much more electronegative than hydrogen, so it pulls the shared electrons towards itself and carries a partial negative charge, while the two hydrogens carry partial positive charges.

Argon has atomic number 18, and a neutral atom has as many electrons as protons, so it has 18 electrons.

X-rays have wavelengths of roughly 0.01 nm to 10 nm, so 1 nm sits right inside the X-ray band. The electromagnetic spectrum runs, from the shortest wavelength to the longest, as gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves.

Meiosis makes gametes that differ from one another, and fertilization joins a gamete from each of two parents, so every offspring gets a new mix of genes.

Work is W = F × d × cos θ, and when the angle θ between force and displacement is 90°, cos 90° = 0, so the work done is zero.

As an object comes in from far away towards C, its real, inverted image moves out from the focus towards C, and the two meet at C. For a concave mirror, an object at infinity forms its image at the focus F, and an object at the centre of curvature…

To just complete a vertical circle, a bob on a string needs a speed of at least √(5gL) at the lowest point, and √(5 × 10 × 0.5) = √25 = 5 m/s. A string can only pull, never push.

Syngamy is the fusion of a male and a female gamete, and since each gamete is haploid, their union gives a diploid zygote.