ATDH - Admission Test for Dental Hygiene Chemical Equations and Reactions Questions and Answers

Question 1

The process of teeth whitening often involves the decomposition of hydrogen peroxide (H₂O₂), which breaks down into water (H₂O) and oxygen gas (O₂). Which of the following correctly balances the chemical equation for this reaction?

Accepted Answer

2H₂O₂ → 2H₂O + O₂

Answer

To balance the equation, the number of atoms of each element must be the same on both sides. The equation 2H₂O₂ → 2H₂O + O₂ has 4 hydrogen atoms and 4 oxygen atoms on the reactant side, and 4 hydrogen atoms and (2+2)=4 oxygen atoms on the product side, satisfying the Law of Conservation of Mass.

Question 2

A patient's saliva helps to neutralize acidic byproducts from plaque bacteria. The reaction of an acid (like HCl from stomach reflux) with a base (like NaOH) to produce a salt (NaCl) and water (H₂O) is a classic example of what type of chemical reaction?

Accepted Answer

Neutralization

Answer

A neutralization reaction is a specific type of double replacement reaction where an acid and a base react to form a salt and water. This process is crucial in the oral cavity for counteracting acids that can lead to enamel erosion.

Question 3

The fundamental principle that requires the number of atoms of each element to be identical on both sides of a chemical equation is known as:

Accepted Answer

The Law of Conservation of Mass

Answer

The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions. Therefore, the mass of the reactants must equal the mass of the products, which is achieved by ensuring the same number of atoms for each element are present on both sides of the equation.

Question 4

In the mouth, salivary amylase is an enzyme that accelerates the breakdown of complex carbohydrates (starch) into simpler sugars. What is the role of salivary amylase in this chemical reaction?

Accepted Answer

A catalyst

Answer

Salivary amylase acts as a biological catalyst. A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Enzymes are proteins that serve as catalysts in biological systems.

Question 5

Phosphoric acid (H₃PO₄) is used in dentistry to etch tooth enamel, while calcium hydroxide (Ca(OH)₂) can be used as a pulp-capping agent. Which of the following are the correct products of the neutralization reaction between these two compounds?

Accepted Answer

Calcium phosphate and dihydrogen monoxide

Answer

This is a double replacement and neutralization reaction. The calcium (Ca²⁺) from the base combines with the phosphate (PO₄³⁻) from the acid to form the salt calcium phosphate (Ca₃(PO₄)₂). The hydrogen (H⁺) from the acid combines with the hydroxide (OH⁻) from the base to form water (H₂O), also known as dihydrogen monoxide. The balanced equation is 2H₃PO₄ + 3Ca(OH)₂ → Ca₃(PO₄)₂ + 6H₂O.

ATDH - Admission Test for Dental Hygiene Practice Test

ATDH - Admission Test for Dental Hygiene Practice Test

ATDH - Admission Test for Dental Hygiene Chemical Equations and Reactions Questions and Answers