Chemistry in Biology Practice

Which statement best explains why a water molecule is considered polar?

• Oxygen and hydrogen share electrons equally, creating no charge difference.

• There is an uneven distribution of electrons between oxygen and hydrogen, leading to slight charges.

• Hydrogen has more protons than oxygen, pulling electrons toward hydrogen.

• Water molecules are ions with full positive and negative charges.

Tags

NGSS.MS-PS1-1

What slight charges develop on the ends of a water molecule due to electron distribution?

• Oxygen end slightly positive; hydrogen end slightly negative.

• Both oxygen and hydrogen ends slightly negative.

• Oxygen end slightly negative; hydrogen end slightly positive.

• Both oxygen and hydrogen ends slightly positive.

Tags

NGSS.MS-PS2-3

How does the strength of hydrogen bonds compare to covalent or ionic bonds?

• Stronger than both covalent and ionic bonds

• Equal in strength to covalent bonds but weaker than ionic bonds

• Weaker than both covalent and ionic bonds but still strong enough to molecules together.

• Strength varies and can be stronger or weaker than covalent bonds

Which statement best defines a mixture?

• A pure substance made of one type of atom chemically bonded

• A material composed of two or more elements or compounds that are physically mixed but not chemically combined

• A liquid that dissolves other substances

• A compound formed by chemical reaction between elements

In a salt–water solution, which component is the solute?

• Water

• Table salt (NaCl)

• Sodium ions only

• Chloride ions only

A student places a crystal of table salt into warm water. Based on the dissolution process, what primarily causes the Na+ and Cl− to separate and spread through the water?

• Heat breaks the ionic bonds without interaction with water molecules.

• The polar water molecules attract the ions, pulling them away from the crystal.

• Gravity pulls the heavier ions to the bottom of the beaker.

• Air bubbles attach to the ions and carry them away.

A solution has a high concentration of H+ ions. Based on the pH scale (0 to 14), which description is most accurate?

• It is basic and has a pH above 7.

• It is acidic and has a pH below 7.

• It is neutral with a pH of exactly 7.

• It cannot be classified without knowing OH− concentration.

According to the pH scale diagram, which pH value represents a neutral solution?

• 5

• 7

• 9

• 14

Which everyday substance is shown as basic on the pH scale?

• Lemon juice

• Milk

• Soap

• Tomato juice

Which statement about basic (alkaline) solutions is correct?

• They contain higher concentrations of H+ ions than pure water and have pH values below 7.

• They contain lower concentrations of H+ ions than pure water and have pH values above 7.

• They contain the same H+ concentration as pure water and have pH equal to 7.

• They have pH values between 1 and 3.