$$6.02 \times 10$$^{23}$$ molecules

Question 1

What is the molecular mass (in daltons) of urea ($$CO(NH_2$)_2$$)? Use the atomic masses: C = 12.01, O = 16.00, N = 14.01, H = 1.01.

Accepted Answer

$$60.06$$ daltons

Question 2

How many grams of urea ($$CO(NH_2$)_2) $$are needed to make 1 liter of a 1M solution?

Accepted Answer

$$60.06$$ grams

Question 3

How many molecules are present in 1 liter of a 1M solution of urea?

Accepted Answer

$$6.02 	imes 10$$^{23}$$ molecules

Question 4

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 5

What type of bond forms between two water molecules due to their polarity?

Accepted Answer

Hydrogen bond

Question 6

If the concentration of $$[OH^-] in a $$solution is $$10^{-8} M$$, what is the pH of the solution?

Accepted Answer

$$pH = 6$$

Question 7

A solution has a pH of 3. How many times greater is its $$[H^+]$$ concentration compared to a solution with pH 5?

Accepted Answer

$$100$$ times greater

Question 8

Which functional group is responsible for the acidic properties of amino acids?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 9

Which of the following molecules is hydrophobic?

Accepted Answer

Methane ($$CH_4)$$

Question 10

Which statement about isomers is correct?

Accepted Answer

Isomers have the same molecular formula but different structural arrangements.

Question 11

Which type of isomerism is illustrated by cis- and trans- forms of 2-butene?

Accepted Answer

Geometric (cis-trans) isomerism

Question 12

Which functional group can act as a base by accepting a hydrogen ion?

Accepted Answer

Amino group ($$-NH_2$)

Question 13

What is the product of $$[H^+]$$ and $$[OH^-]$$ concentrations in pure water at $$25^\circ C$$?

Accepted Answer

$$1.0 	imes 10$$^{-14}$$

Question 14

Which functional group is found in organic phosphates and is important for energy transfer in cells?

Accepted Answer

Phosphate group ($$-$$OPO_3$$^{2-})$$

Question 15

Which of the following is a correct application of the HONC 1234 rule?

Accepted Answer

Nitrogen forms 3 covalent bonds in organic molecules.

Question 16

Which property is shared by both ketone and aldehyde functional groups?

Accepted Answer

Both contain a carbonyl group ($$\u003eC=O)$$

Question 17

Which functional group is responsible for stabilizing protein structure through cross-linking?

Accepted Answer

Sulfhydryl group ($$-SH)$$

Question 18

A patient is given S-ibuprofen for pain relief, but the R-enantiomer is ineffective. What concept does this illustrate?

Accepted Answer

Enantiomers can have different biological activities.

Question 19

Which functional group is nonpolar and often involved in gene expression when attached to DNA?

Accepted Answer

Methyl group ($$-CH_3$)

Question 20

If you add hydrochloric acid ($$HCl) to $$water, what happens to the pH?

Accepted Answer

The pH decreases.

General Biology Study Notes: Carbon Chemistry, Water Structure, and Solution Calculations

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