Eden's World Of Education

11/05/2023

03/11/2022

Phylum Onychophora, or velvet worms, contains approximately 180 species of bilaterally symmetrical, coelomate organisms that somewhat resemble caterpillars. Onychophorans range from 5 mm to 15 cm in length, with homonomous bodies and small heads. The head carries a pair of annulated, fleshy antennae and a pair of small eyes at their bases, with large, chitinous lenses and a well-developed retinal layer, as well as a pair of jaws surrounded by circular lips, and a pair of fleshy oral papillae, also known as slime papillae. The sticky secretions produced by the latter structures are used to capture prey, which includes other small invertebrates. Living species are divided into two families, Peripatidae and Peripatopsidae, which live in mutually exclusive geographical regions; peripatids are circumtropical, while peripatopsids are circumaustral. Members of the two families differ in their number of legs (generally greater in peripatids), the position of their gonopore (on a more posterior body segment in peripatopsids), and their reproductive habits. All of the currently known living species are terrestrial, living mainly in dark, moist microhabitats. Research indicates that they are either modified arthropods or represent a link between annelids and arthropods, most recent molecular phylogenies favor the first hypothesis. (Brusca and Brusca, 2003; Monge-Nájera, 1995; Shapiro, 2012; Zhang, 2011)

25/04/2022

A Science Odyssey Atom Builder

The Atom Builder Guide to Elementary Particles

Diagram of Helium that shows two electrons and a nucleus with 2 protons and 2 neutrons Atoms are constructed of two types of elementary particles: electrons and quarks.
Electrons occupy a space that surrounds an atom's nucleus. Each electron has an electrical charge of -1.

Quarks make up protons and neutrons, which, in turn, make up an atom's nucleus. Each proton and each neutron contains three quarks.

A quark is a fast-moving point of energy. There are several varieties of quarks. Protons and neutrons are composed of two types: up quarks and down quarks.

Each up quark has a charge of +2/3.
Each down quark has a charge of -1/3.
The sum of the charges of quarks that make up a nuclear particle determines its electrical charge.

Protons contain two up quarks and one down quark.
+2/3 +2/3 -1/3 = +1

Neutrons contain one up quark and two down quarks.
+2/3 -1/3 -1/3 = 0

The nucleus is held together by the "strong nuclear force," which is one of four fundamental fources (gravity and electromagnetism are two others). The strong force counteracts the tendency of the positively-charged protons to repel each other. It also holds together the quarks that make up the protons and neutrons.

Note: In addition to electrons and quarks, physicists have identified a number of other subatomic particles. Quantum physics describes the subatomic world as one that cannot be depicted in diagrams -- particles are not dots in space (as depicted in this feature), but are more like "dancing points of energy."

02/02/2022

3) 25 mL of a solution of barium hydroxide on titration with 0.1 molar solution of hydrochloric acid gave titer value of 35 mL. The molarity of barium hydroxide solution was :
(AIEEE 2003)

1) 0.07

2) 0.14

3) 0.28

4) 0.35

Solution:

The reaction involved in the titration is:

Ba(OH)2 + 2HCl -------> BaCl2 + 2H2O

The equation that is used to find the molarity of unknown solutions in titrations is:

M1V1/n1 = M2V2/n2

Where

M1 and M2 are, respectively, the molarities of Ba(OH)2 & HCl solutions.

V1 and V2 are, respectively, the volumes of Ba(OH)2 & HCl solutions.

n1 = Stoichiometric coefficient of Ba(OH)2 = 1

n2 = Stoichiometric coefficient of HCl = 2

Therefore:

molarity of barium hydroxide solution, M1 = (M2V2/n2) x (n1/V1) = (0.1 x 35 / 2) x (1/25) = 0.07 M

Conclusion:

The correct option is '1'.

02/02/2022

2) The density (in g mL–1) of a 3.60 M sulphuric acid solution that is 29% H2SO4 (Molar mass = 98 g mol–1) by mass will be:
(AIEEE 2007)

1) 1.45

2) 1.64

3) 1.88

4) 1.22

Solution:

The relation between Molarity, M and mass percent (%) is given by:

M = (% x 10 x d) / MW

Where:

MW = molecular weight of solute

d = density of solution

Therefore:

d = M x MW / (% x 10) = 3.60 x 98 / 29 x 10 = 1.216 g mL-1

Conclusion:

The correct option is '4'.

02/02/2022

1) Two solutions of a substance (non electrolyte) are mixed in the following manner. 480 mL of 1.5 M first solution + 520 mL of 1.2 M second solution. What is the molarity of the final mixture?
(AIEEE 2005 - equivalent to IIT JEE MAIN)

1) 1.20 M

2) 1.344 M

3) 1.50 M

4) 2.70 M

Logic & Solution:

Molarity of a mixture, Mmix can be calculated by:

Mmix = (M1V1 + M2V2) / (V1 + V2) = (1.5 x 480) + (1.2 x 520)/(480 + 520) = 720+624/1000 = 1.344 M

Conclusion:

The correct option is '2'.