Chemical Reactions Quiz: MCQ Exam!

2.

.O {font-size:149%;} You can tell a chemical reaction because it always produces …

A different substance
Reactants
A change of state
Water

Correct Answer

A. A different substance

Explanation

A chemical reaction can be identified by the production of a different substance. This means that the reactants, which are the substances undergoing the reaction, combine and rearrange their atoms to form new substances with different chemical properties. This change in composition is a key characteristic of chemical reactions and distinguishes them from physical changes, such as changes in state or the formation of water.

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3.

Slide 5 To balance a chemical equation, you should change only the…

Subscripts
Coefficients
Chemical formulas
Location of the arrow

Correct Answer

A. Coefficients

Explanation

To balance a chemical equation, you should change only the coefficients. Coefficients are the numbers that are placed in front of the chemical formulas to balance the number of atoms on both sides of the equation. By adjusting the coefficients, you can ensure that the same number of atoms of each element is present on both sides of the equation, maintaining the law of conservation of mass. Changing the subscripts would alter the chemical formula, which would represent a different compound altogether. The location of the arrow represents the direction of the reaction and does not affect the balancing of the equation.

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4.

Slide 6 .O {font-size:149%;} If iron combines with oxygen to make iron oxide, the reactants are…

Iron oxide
Iron and iron oxide
Iron and oxygen
Oxygen and iron oxide

Correct Answer

A. Iron and oxygen

Explanation

When iron combines with oxygen to form iron oxide, the reactants involved in the chemical reaction are iron and oxygen. Iron reacts with oxygen to produce iron oxide.

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5.

Slide 7 How many carbon atoms are there in C12H22O11?

6
12
18
45

Correct Answer

A. 12

Explanation

The formula C12H22O11 represents a molecule of sucrose, which is a disaccharide made up of 12 carbon atoms. Therefore, the correct answer is 12.

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6.

Slide 8 How many oxygen atoms are in the product of this equation: 2H2 + O2 --> 2H2O

2
4
8
12

Correct Answer

A. 2

Explanation

In the given equation, 2H2 + O2 -> 2H2O, the coefficient in front of O2 is 1. This means that there is only one molecule of O2 involved in the reaction. Since each molecule of O2 contains two oxygen atoms, the total number of oxygen atoms in the product (2H2O) is also 2.

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7.

Slide 9 .O {font-size:149%;} Which one of the following is a chemical equation?

Ice + heat --> water
Iron + oxygen --> rust
CO2
C + O2 --> CO2

Correct Answer

A. C + O2 --> CO2

Explanation

The given answer, C + O2 --> CO2, is a chemical equation because it represents a chemical reaction between carbon (C) and oxygen (O2) to form carbon dioxide (CO2). In a chemical equation, the reactants are written on the left side of the arrow and the products are written on the right side. In this equation, C and O2 are the reactants, and CO2 is the product. The arrow indicates the direction of the reaction, showing the transformation of the reactants into the products.

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8.

.O {font-size:149%;} Balance the following equation: Ag + O2 --> Ag2O

Put a 2 in front of Ag
Add a subscript 2 to the end of Ag2O
Add a 4 in front of Ag and a 2 in front of Ag2O
Add a 2 in front of Ag and a 1 in front of Ag2O

Correct Answer

A. Add a 4 in front of Ag and a 2 in front of Ag2O

Explanation

To balance the equation Ag + O2 --> Ag2O, you need to ensure that the number of each type of atom is the same on both sides of the equation. By adding a 4 in front of Ag and a 2 in front of Ag2O, you have balanced the equation. This is because now there are 4 atoms of Ag on both sides and 2 atoms of O on both sides, resulting in a balanced equation.

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9.

.O {font-size:149%;} In a chemical equation, the arrow means what?

A reaction is happening.
The two sides are equal.
The products flow into reactants.
The equation is balanced.

Correct Answer

A. A reaction is happening.

Explanation

The arrow in a chemical equation indicates that a reaction is happening. It shows the direction in which the reactants are transforming into products. The arrow points from the reactants to the products, indicating the flow of the reaction.

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10.

.O {font-size:149%;} The reactants include 7 grams of C and 4 grams of O. What is the total amount of C and O in the products?

7 grams
4 grams
11 grams
None

Correct Answer

A. 11 grams

Explanation

The total amount of C and O in the products is 11 grams because the question states that the reactants include 7 grams of C and 4 grams of O. When these reactants undergo a chemical reaction, they will combine to form products. Since the reactants are completely consumed in the reaction, the total amount of C and O in the products will be equal to the sum of the amounts in the reactants, which is 7 grams + 4 grams = 11 grams. Therefore, the correct answer is 11 grams.

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11.

.O {font-size:149%;} Who first determined that the masses of the reactants and products must be the same?

Pasteur
Archimedes
Galileo
Lavoisier

Correct Answer

A. Lavoisier

Explanation

Lavoisier was the first to determine that the masses of the reactants and products must be the same. He conducted experiments on chemical reactions and observed that no mass was gained or lost during the process. This led him to propose the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Lavoisier's work laid the foundation for modern chemistry and our understanding of the conservation of mass in chemical reactions.

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12.

.O {font-size:149%;} If you try to balance an equation by changing subscripts you change…

The number of molecules of product
The identity of the compound
The atomic number
The mass of the reactants

Correct Answer

A. The identity of the compound

Explanation

When balancing an equation by changing subscripts, you are altering the chemical formula of the compound. This means that you are changing the arrangement and type of atoms in the compound, thus changing its identity. The number of molecules of the product, the atomic number, and the mass of the reactants may be affected by balancing the equation, but the primary change is the identity of the compound itself.

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Chemical Reactions Quiz: MCQ Exam!

Which one of the following represents a physical change?

Quiz Preview

.O {font-size:149%;} You can tell a chemical reaction because it always produces …

Slide 5 To balance a chemical equation, you should change only the…

Slide 6 .O {font-size:149%;} If iron combines with oxygen to make iron oxide, the reactants are…

Slide 7 How many carbon atoms are there in C12H22O11?

Slide 8 How many oxygen atoms are in the product of this equation: 2H2 + O2 --> 2H2O

Slide 9 .O {font-size:149%;} Which one of the following is a chemical equation?

.O {font-size:149%;} Balance the following equation: Ag + O2 --> Ag2O

.O {font-size:149%;} In a chemical equation, the arrow means what?

.O {font-size:149%;} The reactants include 7 grams of C and 4 grams of O. What is the total amount of C and O in the products?

.O {font-size:149%;} Who first determined that the masses of the reactants and products must be the same?

.O {font-size:149%;} If you try to balance an equation by changing subscripts you change…