b. hydrogen. d. nitrogen. 3. In the following equation, name the reactants: NaCI
ID: 150568 • Letter: B
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b. hydrogen. d. nitrogen. 3. In the following equation, name the reactants: NaCI-Na+a a. Na b. C e. NaCl d. Both a and b are correct 4. A covalent bond in which electrons are not shared equally is called polar. b. normal. c. nonpola d. neutral 5. Refer to Figure 2.3. Which element has the same number of valence electrons as nitrogen (N)? a. carbon (C) b. phosphorus (P) c. neon (Ne) d. oxygen (O) 2.2 Water's Importance to Life 6. Water flows freely but does not separate into individual molecules because water is a. cohesive. b. hydrophilic. c. hydrophobic. d. adhesive. 7. Compounds having an affinity for water are said to be a. cohesive c. hydrophobic. d. adhesive. b. hydrophilic 8. Water freezes from the top down because a. water has a high surface tension. b. ice has a high heat capacity c. ice is less dense than water d. ice is less cohesi ve than water 6Explanation / Answer
3. In this reaction breakdown of NaCl to Na+ and Cl- is taking place . Therefore the reactant here is NaCl.
4. Polar. A polar covalent bond is between atoms with considerable difference in electronegativities. For example O-H bond in water is polar covalent. Due to difference in electronegativities, the shared electron pair spend more time near oxygen than hydrogen. There is slight charge separation with oxygen having a partial negative charge and hydrogen having partial positive charge.
5. Nitrogen has 5 valence electrons 2s2 2p3. Phosphrous also has the 5 valence electrons 3s2 3p3
6. Water is cohesive i.e water molecules are connected to each other via hydrogen bonds which makes them stick to each other.
7. Compounds having an affinity for water are called hydrophilic i.e water loving. Polar molecules are hydrophilic as they can formed hydrogen bonds with water molecules.
8. Ice is less dense than water. This is because ice is a crystal with regularly spaced molecules. The spaces between water molecule is more in ice as compared to liquid water. Therefore ice is less dense than water. Less dense substance (ice) tends to float when placed in a more dense substance (water).
During cooling , Air cools down more quickly than water. The surface water is in direct contact with cool air and freezes first. Since ice is denser than liquid water it remains at the top.
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