Nokea
What are buffers?
- A. Proteins
- B. Solutions that resist changes in pH
- C. Catalysts in a reaction
- D. Inhibitors in a reaction
Correct Answer: B
Rationale: Buffers are solutions that resist changes in pH by neutralizing small amounts of acids or bases that may be added to them. They help maintain a stable pH environment and are commonly used in various biological and chemical processes to prevent drastic changes in acidity or alkalinity. Buffers do not act as catalysts or inhibitors in reactions. Their main purpose is to stabilize pH levels and ensure a relatively constant pH within a system, making them essential in maintaining the proper conditions for many biological reactions and processes.
You may also like to solve these questions
What is the density of a block on your desk that acts as a paperweight? The block measures 3cm by 4cm by 6cm and has a mass of 184.32g.
- A. 13.27 g/cm3
- B. 2.56 g/cm3
- C. 0.39 g/cm3
- D. None of the above.
Correct Answer: B
Rationale: To calculate density, you use the formula: Density = Mass/Volume. First, calculate the volume of the block by multiplying its dimensions: 3cm x 4cm x 6cm = 72 cm3. Next, divide the mass (184.32g) by the volume (72 cm3) to find the density. Density = 184.32g / 72 cm3 = 2.56 g/cm3. Therefore, the correct answer is B, with a density of 2.56 g/cm3.
What is the building block of proteins?
- A. Lipids
- B. Amino acids
- C. DNA
- D. Cells
Correct Answer: B
Rationale: Amino acids are the fundamental building blocks of proteins. Proteins are large biomolecules made up of one or more chains of amino acids. Each amino acid contains an amine group, a carboxylic acid group, and a side chain specific to each amino acid. When amino acids link together through peptide bonds, they form proteins. Lipids are a different type of biomolecule that includes fats, oils, and phospholipids. DNA is a nucleic acid that carries genetic information but is not directly involved in the structure of proteins. Cells are the basic structural and functional units of living organisms, not the building blocks of proteins.
Which of the following exhibits the most molecular interactions?
- A. Solid
- B. Liquid
- C. Gas
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'Solid.' In solids, molecules are closely packed, leading to strong intermolecular forces and the highest number of molecular interactions among the given options. This close proximity results in strong attractions between molecules, creating a high number of interactions. In contrast, liquids have weaker intermolecular forces due to more freedom of movement among molecules, leading to fewer interactions compared to solids. Gases have the least molecular interactions as their molecules are widely dispersed and have minimal attraction to each other, resulting in the lowest number of interactions.
What is the general reaction for neutralizing acids and bases?
- A. Acid + base → water + salt
- B. Base + water → acid + salt
- C. Salt + water → acid + base
- D. Acid + base → water + salt
Correct Answer: D
Rationale: The correct general reaction for neutralizing acids and bases is when an acid reacts with a base, it forms water and a salt. This reaction is commonly known as a neutralization reaction. The hydrogen ions from the acid combine with the hydroxide ions from the base to form water, while the anion from the acid combines with the cation from the base to form a salt.
What can be predicted by using the periodic table?
- A. The properties of each of the elements
- B. The charges of polyatomic ions
- C. The number of isotopes in each element
- D. The potential for the discovery of new elements
Correct Answer: A
Rationale: The periodic table is a fundamental tool in chemistry that organizes elements based on their properties. By using the periodic table, scientists can predict the properties of each element. The arrangement of elements in the table groups together elements with similar characteristics, allowing for the prediction of various properties such as reactivity, atomic size, and electronegativity. These predictions are possible because elements in the same group or period exhibit similar chemical behaviors. Therefore, the correct answer is A: The properties of each of the elements.