Solutions and pH

A molecule, such as water, that has partially charged positive and negative areas is

• neutral

• universal

• polar

• nonpolar

Answer explanation

A molecule like water has regions with partial positive and negative charges due to its shape and the electronegativity of oxygen. This characteristic makes it a polar molecule, as opposed to neutral or nonpolar substances.

What would be the best solution to add to a strong base to neutralize it?

• strong acid

• strong base

• weak base

• weak acid

Answer explanation

To neutralize a strong base, adding a strong acid is the best solution. The strong acid will react with the strong base to form water and a salt, effectively reducing the pH and achieving neutralization.

Bases cause litmus paper to turn blue.

• True

• False

Answer explanation

True. Bases are substances that increase the pH of a solution, and when litmus paper is exposed to a basic solution, it changes color to blue, indicating the presence of a base.

In a neutral solution the pH is always equal to ___.

• 7

• Indicators

• Sour

• Bitter

• Supersaturated

Answer explanation

In a neutral solution, the concentration of hydrogen ions equals that of hydroxide ions, resulting in a pH of 7. This is the standard value for neutrality in the pH scale.

Acids contain high amounts of ____ ions.

• Hydrogen (H+)

• Indicators

• Sour

• Bitter

• Supersaturated

Answer explanation

Acids are defined by their ability to donate protons (H+ ions) in a solution. Therefore, they contain high amounts of hydrogen ions, making 'Hydrogen (H+)' the correct answer.

A solution with a pH of ____ is a strong base.

• 14

• Indicators

• Sour

• Bitter

• Supersaturated

Answer explanation

A solution with a pH of 14 is considered a strong base, as the pH scale ranges from 0 to 14, with 14 being the most alkaline. Therefore, the correct answer is 14.

Saltwater is an example of a solution. Compared to the salt, which term best describes the water in the solution? 

• Solute

• Solvent

• mixture

• suspension

Answer explanation

In a solution, the solute is the substance being dissolved (salt), while the solvent is the substance doing the dissolving (water). Therefore, in saltwater, water is best described as the solvent.

A chemist is working with a liquid substance that tastes bitter, feels slippery, and conducts an electric current. Which of the following is the chemist most likely working with? 

• a salt

• a base

• an acid

• distilled water

Answer explanation

The chemist is most likely working with a base, as bases are characterized by a bitter taste, slippery feel, and the ability to conduct electricity due to the presence of ions.

Human blood is slightly basic. Where would you add human blood to the diagram? 

• between ammonia and oven cleaner? 

• between water and baking soda

• between lemon juice and vinegar

• between water and ammonia

Answer explanation

Human blood is slightly basic, with a pH around 7.4. This places it between water (neutral, pH 7) and baking soda (slightly basic, pH around 8.4), making 'between water and baking soda' the correct choice.

Four substances were tested for pH, lemon juice (pH 2), baking soda (pH 9), bleach (pH 12), and milk (pH 6). Which of the following correctly lists the substances from most basic to acidic?

• lemon juice, milk, baking soda, bleach

• bleach, baking soda, milk, lemon juice

• milk, lemon juice, baking soda, bleach

• baking soda, bleach, lemon juice, milk

Answer explanation

To order the substances from most basic to acidic, we compare their pH values: bleach (pH 12), baking soda (pH 9), milk (pH 6), and lemon juice (pH 2). Thus, the correct order is bleach, baking soda, milk, lemon juice.

Tags

NGSS.MS-PS1-2