Question

we: In living cells, the weakest bond between wo more som a) ionic bond b) covalent bond c) polar bond d) metallic bond hydrogen bond Dor more atoms is the 41, .Tonic bonds are formed when 2) atoms share electrons D electrons are completely transferred from one stom to another c) a pair of electrons is shared unequally by two stom d) hydrogen forms bonds with negatively charged atoms in the sun e) two or more atoms lose electrons at the same time y charged atoms in the same or different molecule na molecule of nitrogen, three pairs of clectrons are shared by two nitrogen atoms. of bond that is formed would be an example of a(n) a) single covalent bond b) double covalent bond triple covalent bond d) polar covalent bond e) hydrogen bond 49. If a pair of electrons is unequally shared between two atoms, an a) single covalent bond b) double covalent bond c) triple covalent bond. d) polar covalent bond e) hydrogen bond 44. Elements that have full outer shells of electrons a) will form many compounds b) will normally form anions c) will normally form cations J) frequently form hydrogen bonds are inert 15. Creation occurs when a blood cell is placed in a) isotonic solution b) hypertonic solution hypotonic solution d) merotonic solution e) none of the above

Answer 1

40. Ionic bond is a bond that occurs due to loss or gain of electrons. Covalent bond is formed by mutual sharing of electrons. Polar covalent bond is bond cause by unequal sharing of electrons due to electronegativity differences. Metallic bonds occur due to sharing of electrons that are detached from many positive ions. These electrons act as glue to stick all the positively charged electrons. Hydrogen bonds are bonds between an electropositive hydrogen atom of one molecule with oxygen or any other more electronegative atom of another molecule. Metallic bonds are weaker than ionic and covalent bond while hydrogen bonds are weaker than metallic bonds. Hydrogen bonds are not actually bond but just attraction between atoms while metallic bonds are bond between ions of metals.

Right choice: e) Hydrogen bonds.

41. When atoms share electrons, covalent bonds are formed. When atoms lose or gain electrons, they form ionic bonds to become positively or negatively charged ions. Positively charged ions are formed when electrons are completely transferred to another atom. Polar covalent bonds are formed by unequal sharing of electrons. Hydrogen bonds are formed between hydrogen of one molecule with an electronegative atom of same or different molecule. Metallic bonds are formed between lost electrons of many positively charged ions.

Right choice: b) Electrons are completely transferred one atom to another atom.

42. Nitrogen atom has five electrons in its outermost shell. The first two electrons are in one orbital, making them complete orbitals. The other 3 electrons are single electrons in three separate orbitals. Hence it needs 3 electrons to complete its outermost shell. Thus, they will share 3 electrons with another nitrogen atom to complete its electronic shell. Neither nitrogen atom in nitrogen molecule will prefer to lose any electrons. Instead they will mutually share electrons to form three separate covalent bonds. Such bonds are called triple-covalent bonds. Single covalent bond is formed by mutual sharing of two electrons between two atoms. If four atoms are shared, a double covalent bond is formed. Bothe nitrogen atoms have equal electronegativities. Hence, they will not form polar covalent bond. There is no hydrogen in a nitrogen atom to form hydrogen bond.

Right choice: c) Triple covalent bond.

43. Unequal sharing of electrons results in polar covalent bond. One atom will be more electronegative pulling the electrons towards itself and gaining net negative charge. The other atom will be less electronegative and will have a net positive charge. Single, double and triple covalent bonds will have mutual sharing of one, two and three pairs of electrons. Hydrogen bond is formed between a lesser electronegative Hydrogen and a more electronegative atom in same or different molecule.

Right choice: d) polar covalent bond.

44. If an element or atom has 8 electrons in its outermost shell, it will not need to lose/gain or share electrons with other atoms to become stable. Such elements with complete outermost shells are inert and hence, completely stable. Anions are positively charged ions formed by gain of electrons while cations are formed by loss of electrons. Water molecules frequently form hydrogen bonds between oxygen and hydrogen. Inert atoms do not form compounds, which have 2 or more atoms.

Right choice: e) inert.

45. Crenation is notched or scalloped appearance of cell with spikes/projections being formed or extended from the membrane. Crenation is caused by loss of water from the RBC. When RBC are placed in hypertonic solution (Higher concentration of solutes in solution as compared to intracellular RBC compartment), water will exit the RBC by osmosis into the hypertonic solution. This will cause dehydration of RBC resulting in crenation. RBC placed in hypotonic solution will see water entering the cell, leading to cell swelling. There is no change in cell shape in isotonic solution (normal round shape). There is no merotonic solution.

Right choice: b) Hypertonic solution.