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Calculate how many electrons make a total charge of 1 coulomb.
Magnitude of electron charge \(e=1.60\times10^{-19}\) C.
\(6.25\times10^{18}\) electrons.
State
The near point, or least distance of distinct vision, is about \(25\,\mathrm{cm}\) from the eye. The far point is at infinity.
Which mirror can form an upright, enlarged image?
A concave mirror forms a virtual, erect and magnified image when the object is placed between its pole and principal focus. Plane and convex mirrors give erect images but do not enlarge them.
A concave mirror, with the object between P and F.
How did Mendel's monohybrid crosses demonstrate dominant and recessive traits?
Mendel crossed true-breeding tall peas (TT) with dwarf peas (tt). Every F1 plant was tall (Tt), showing that tallness is dominant and masks dwarfness. Selfing F1 plants produced F2 genotypes TT, Tt, Tt and tt, giving approximately three tall plants to one dwarf. Reappearance of dwarfness showed that its factor remained present but was recessive.
Differentiate binary fission and multiple fission.
In binary fission, one parent nucleus divides once and the cell separates into two daughter organisms; Amoeba is an example. In multiple fission, the nucleus divides repeatedly before cytoplasm partitions, producing many daughter cells at once; Plasmodium is an example. Both are asexual and usually produce genetically similar offspring.
Which brain region maintains posture and body equilibrium?
The cerebellum integrates information from the inner ear, eyes and muscles and coordinates muscle contractions needed for posture, precision and balance.
Cerebellum.
For what purposes do organisms use raw materials obtained from outside?
Food supplies energy and building material for growth and repair. Oxygen enables release of energy from food in aerobic respiration. Water acts as a reaction medium and transport solvent; mineral ions support structure, enzymes and regulation. Autotrophs additionally use carbon dioxide and water to synthesise carbohydrates.
External materials provide energy, matter for growth/repair, and media or reactants for metabolism.
Draw and count the structural isomers of pentane, \(\ce{C5H12}\).
The same molecular formula can have three different carbon skeletons:
Moving the branch further in the second structure only reverses the chain, so it does not give another isomer.
Three structural isomers.
Why is sodium stored below kerosene?
Sodium is highly reactive. It reacts vigorously with oxygen and moisture and may ignite because the reaction releases much heat. Kerosene keeps sodium away from air and water and therefore prevents accidental reaction.
Kerosene isolates sodium from oxygen and moisture.
Name
A reactive metal displaces hydrogen from a dilute acid, so the gas is hydrogen.
Bring a burning splint close to the collected gas. Hydrogen burns with a characteristic pop sound, confirming its presence.