# Section C Review Pg.153-179

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Questions: 37 | Attempts: 154  Settings  Review of Section C Law of Conservation of Matter.

• 1.

### What is the molar mass of Carbon?

• A.

6 g/mol

• B.

12.01 g/mol

• C.

19.00 g/mol

• D.

1.01 g/mol

B. 12.01 g/mol
Explanation
The molar mass of a substance is determined by the average atomic mass according to the periodic table. The molar mass of carbon is 12.01 g/mol

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• 2.

### What is the molar mass of CH4 (methane)?

• A.

12.01 g/mol

• B.

13.02 g/mol

• C.

16.05 g/mol

• D.

32.10 g/mol

C. 16.05 g/mol
Explanation
The molar mass of a substance is determined by the average atomic mass according to the periodic table. There is 1 carbon in CH4 (methane) and 4 hydrogen:
Carbon 1 (12.01) + Hydrogen 4(1.01) = 16.05 g/mol

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• 3.

### What is the molar mass of (NH4)2CO3 (Ammonium carbonate)?

• A.

96.11 g/mol

• B.

82.10 g/mol

• C.

106.11 g/mol

• D.

43.01 g/mol

A. 96.11 g/mol
Explanation
Molar mass is the mass of one mole of the substance. The molar mass of a substance is determined by the average atomic mass according to the periodic table. CAUTION: The parentheses indicates that everything within the parentheses is MULTIPLIED by the subscript outside of the parentheses. This means there are 2 nitrogen, 8 hydrogen (4 x 2), 1 carbon and 3 oxygen in this compound.
Nitrogen 2(14.01) + Hydrogen 8 (1.01) + Carbon 1 (12.01) + Oxygen 3(16.00) = 96.11 g/mol

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• 4.

### What is the molecular mass of Cu3(PO4)2?

• A.

253.49 g/mol

• B.

380.59 g/mol

• C.

110.22 g/mol

• D.

348.59 g/mol

B. 380.59 g/mol
Explanation
Molar mass is the mass of ONE mole of a substance regardless of how many moles there are in the equation. CAUTION: The parentheses indicates that everything within the parentheses is MULTIPLIED by the subscript outside of the parentheses.
This means there are 3 Coppers, 2 Phosphorus, 8 oxygen:
Copper 3 (63.55) + Phosphorus 2(30.97) + 8 (16.00) = 380.59 g/mol

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• 5.

### What is the molecular mass of Aluminum nitrate Al(NO3)3 from this equation: 2Al(s)   + 3Fe(NO3)2(aq)   à 3Fe(s)  + 2Al(NO3)3(aq)

• A.

213.01 g/mol

• B.

335.98 g/mol

• C.

56.99 g/mol

• D.

141.01 g/mol

A. 213.01 g/mol
Explanation
(s) means solid and (aq) means aqueous.
Molar mass is the mass of ONE mole of a substance regardless of how many moles there are in the equation. So, ignore the “2” in front of Al(NO3)3
CAUTION: The parentheses indicates that everything within the parentheses is MULTIPLIED by the subscript outside of the parentheses.
This means there is 1 Aluminum, 3 Nitrogen, 9 oxygen (3 x 3)
The molar mass of a substance is determined by the average atomic mass according to the periodic table.
Aluminum 1 (26.98) + Nitrogen 3 (14.01) + Oxygen 9 (16.00) = 213.01 g/mol

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• 6.

### What coefficients will balance the following equation H2 + O2 --->  H2O

• A.

2,2,1

• B.

2,1,2

• C.

4,1,2

• D.

2,2,2

B. 2,1,2
Explanation
The equation represents the reaction between hydrogen gas (H2) and oxygen gas (O2) to form water (H2O). In order to balance the equation, the number of atoms of each element on both sides of the equation must be equal. The equation is balanced when there are 2 molecules of hydrogen gas, 1 molecule of oxygen gas, and 2 molecules of water. Therefore, the coefficients that will balance the equation are 2, 1, and 2.

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• 7.

### What coefficients will balance the following equation Al  + O2  --> Al2O3

• A.

1,3,2

• B.

4,3,2

• C.

2,2,2

• D.

2,1,3

B. 4,3,2
Explanation
The equation represents the reaction between aluminum (Al) and oxygen (O2) to form aluminum oxide (Al2O3). In order to balance the equation, the number of atoms of each element on both sides of the equation must be equal. By examining the equation, it can be seen that there are 4 Al atoms on the left side and 2 Al atoms on the right side. To balance the Al atoms, a coefficient of 2 is needed in front of Al on the left side. Similarly, there are 3 O atoms on the left side and 3 O atoms on the right side, so no coefficient is needed for O2. Finally, there are 2 O atoms in Al2O3 on the right side, so a coefficient of 2 is needed in front of Al2O3 on the right side. Therefore, the coefficients that balance the equation are 2, 3, 2.

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• 8.

### What coefficients will balance the following equation AgNO3  +  NaCl  ---->  AgCl   +   NaNO3

• A.

2,2,2,1

• B.

1,1,1,1

• C.

1,2,1,2

• D.

2,1,2,1

B. 1,1,1,1
Explanation
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• 9.

### What coefficients will balance the following equation K   +   H2O ----->    KOH   +   H2

• A.

1,1,1,1

• B.

2,2,2,1

• C.

2,1,2,1

• D.

1,2,1,2

B. 2,2,2,1
Explanation
It help a lot when you list your reactants and your products.

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• 10.

### What coefficients will balance the following equation Hg  +  O2  ---->  HgO

• A.

1,1,1

• B.

2,2,1

• C.

2,1,2

• D.

1,2,2

C. 2,1,2
Explanation
In the reactants side, I have 1 mercury atom and 2 Oxygen atoms, so I need to have the same in the products side, a number 2 in front of HgO will give 2 Oxygen, but also gives me 2 Hg, so now I need to add a 2 in front of my Hg in the reactant side to have 2,1,2

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• 11.

### A balanced chemical equation shows the proportions of reactants and products necessary for

• A.

The reaction to occur

• B.

Mass to be conserved.

• C.

Energy use to be minimized.

• D.

Electrolysis to occur.

A. The reaction to occur
Explanation
When we balance an equation we know how much reactants we need for the reaction to occur. It the same as writing a recipe (one cup of rice needs two cups of water, try it!).

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• 12.

### A chemical equation is balanced by changing or adding

• A.

Chemical symbols

• B.

Subscripts

• C.

Coefficients

• D.

Reactants

C. Coefficients
Explanation
The coefficients (number in front of atoms or molecules)are the only item that can be changed when balancing chemical equations.

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• 13.

### What happens in a chemical reaction?

• A.

Atoms are destroyed

• B.

Atoms are created

• C.

Atoms are rearranged

• D.

Atoms are heated or cooled

C. Atoms are rearranged
Explanation
Remember the Law of Conservation of matter: Matter cannot be created nor destroyed, although it may be rearranged.

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• 14.

### A substance that undergoes a change in a chemical reaction is

• A.

A product

• B.

A chemical

• C.

A reactant

• D.

An enzyme

C. A reactant
Explanation
A reactant (left to the --->)is the substance that undergoes changes.

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• 15.

### What are the percent composition for SF2?

• A.

55 % Sulfur and 45% Fluorine

• B.

45.76% Sulfur and 54.39 % Fluorine

• C.

33% Sulfur and 67% Fluorine

• D.

49.2 % Sulfur and 50.8 % Fluorine

B. 45.76% Sulfur and 54.39 % Fluorine
Explanation
First find molar mass: Sulfur 32.06 + Fluorine 2 (19) = 70.06 g
Sulfur percentage: (32.06 divided by the molar mass 70.06) x 100% = 45.76%
Fluorine percentage (38 divided by 70.06) x 100 % = 54.39%

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• 16.

### What is the percent composition of Ethyne? C2H2?

• A.

92.31% Carbon and 7.76% Hydrogen

• B.

82% Carbon and 18% Hydrogen

• C.

82.7% Carbon and 17.3 % Hydrogen

• D.

90% Carbon and 14 % Hydrogen

A. 92.31% Carbon and 7.76% Hydrogen
Explanation
The percent composition of a compound refers to the mass percentage of each element in the compound. In the case of Ethyne (C2H2), there are two carbon atoms and two hydrogen atoms. To calculate the percent composition, we need to determine the molar mass of each element and divide it by the molar mass of the compound, then multiply by 100.

The molar mass of carbon (C) is 12.01 g/mol, and the molar mass of hydrogen (H) is 1.01 g/mol. The molar mass of Ethyne (C2H2) is (2 * 12.01 g/mol) + (2 * 1.01 g/mol) = 26.04 g/mol.

To calculate the percent composition of carbon, we divide the molar mass of carbon by the molar mass of Ethyne and multiply by 100: (2 * 12.01 g/mol) / 26.04 g/mol * 100 = 92.31%.

To calculate the percent composition of hydrogen, we divide the molar mass of hydrogen by the molar mass of Ethyne and multiply by 100: (2 * 1.01 g/mol) / 26.04 g/mol * 100 = 7.76%.

Therefore, the correct answer is 92.31% carbon and 7.76% hydrogen.

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• 17.

### What is the percentage of Sulfur in SF2?

• A.

32.06 % Sulfur

• B.

25% Sulfur

• C.

45.15 % Sulfur

• D.

62.67 % Sulfur

C. 45.15 % Sulfur
Explanation
The correct answer is 45.15% Sulfur. This means that in SF2, 45.15% of the compound's mass is made up of sulfur.

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• 18.

### What is the empirical formula for a compound that contains 1.67 mole Carbon and 5.01 Moles of Hydrogen

• A.

CH

• B.

CH2

• C.

C2H3

• D.

CH3

D. CH3
Explanation
Empirical formula will always be whole numbers. Divide each moles of Carbon and Hydrogen by 1.6 = Carbon 1 and Hydrogen 3.

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• 19.

### What is the empirical formula for a compound that contains 37.69% Na and 62.31 % Fluorine?

• A.

NaF3

• B.

Na2F

• C.

NaF

• D.

NaF2

D. NaF2
Explanation
Change percent to grams: 37.69 g of Na and 62.31 g of Fluorine.
Empirical formula is the simplest whole number ratio of moles.
Change grams to moles (divide by molar mass)
Na: 37.69 / 22.99 g = 1.639 moles
F : 62.31 g/19.00 g = 3.279 moles
Divide each by 1.639: Na 1 and F 2 = NaF2

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• 20.

### What is the empirical formula for: 85.60% C and 14.40% H?

• A.

C2H3

• B.

CH2

• C.

CH3

• D.

C2H4

B. CH2
Explanation
Change percent to grams: 85.6 g C and 14.4 g Hydrogen.
Empirical formula is the simplest whole number ratio of moles.
Change grams to moles (divide by molar mass).
C: 85.6 / 12.01 = 7.127 moles
H : 14.4 g/1.01 = 14.25 moles
Divide by 7.127: C 1 and H 2

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• 21.

### What does the Law of Conservation of Matter refer to?

• A.

Matter can not be created or destroyed.

• B.

Matter can be created but can not be destroyed.

• C.

Matter can be destroyed but not created.

A. Matter can not be created or destroyed.
Explanation
The Law of Conservation of Matter states that matter cannot be created or destroyed, but it can only change forms or be rearranged. This means that the total amount of matter in a closed system remains constant over time. This principle is a fundamental concept in chemistry and physics.

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• 22.

### What is Matter?

Anything that has mass.
Explanation
The correct answer is "Anything that has mass." This definition accurately describes matter, as it encompasses all physical substances and objects that occupy space and have mass. Matter can exist in various forms, such as solids, liquids, and gases, and it is the fundamental building block of the universe.

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• 23.

### What side of the equation are the reactants on?

• A.

Right

• B.

Left

• C.

Middle

• D.

Both.

B. Left
Explanation
The reactants in a chemical equation are typically written on the left side. This is because the left side of the equation represents the starting materials or substances that undergo a chemical reaction. The products of the reaction are then written on the right side of the equation. Therefore, the correct answer is "Left."

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• 24.

### What are the reactants in the following equation? H2 + O → H2O

• A.

Hydrogen

• B.

Oxygen

• C.

Water

• D.

Hydrogen and Oxygen

D. Hydrogen and Oxygen
Explanation
The reactants in the given equation are hydrogen and oxygen. This is indicated by the presence of H2 and O on the left side of the arrow. These are the substances that will undergo a chemical reaction to produce water (H2O) as the product.

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• 25.

### How many atoms of N are in the following molecule? NH3

• A.

1

• B.

2

• C.

3

• D.

0

A. 1
Explanation
The molecule NH3 consists of one nitrogen atom (N), which is indicated by the chemical formula. Therefore, there is 1 atom of N in the molecule NH3.

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• 26.

### How many atoms of Fe are in the following molecule? Fe2O3

• A.

0

• B.

1

• C.

2

• D.

3

C. 2
Explanation
The molecule Fe2O3 contains two atoms of Fe. This is because the subscript 2 indicates that there are two atoms of Fe present in the molecule.

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• 27.

### Is the following equation balanced? NH3 + HCl -->   NH4Cl          (yes or no)

Yes
Explanation
The given equation is balanced because the number of atoms of each element is equal on both sides of the equation. In this equation, there is one nitrogen (N) atom, three hydrogen (H) atoms, and one chlorine (Cl) atom on both the reactant and product sides. Therefore, the equation is balanced.

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• 28.

### What are the correct coefficients needed to balance the following equation? ____Al + _____ O2 --> ____ Al2O3

• A.

2,3,4

• B.

1,3,2

• C.

4,3,2

• D.

4,2,3

C. 4,3,2
Explanation
To balance the equation, we need to ensure that there is an equal number of atoms on both sides. In this case, we have 2 Al atoms on the left side, so we need 2 Al atoms on the right side. Similarly, we have 3 O atoms on the left side, so we need 3 O atoms on the right side. Finally, we have 4 O atoms on the right side, so we need 4 O atoms on the left side. Therefore, the correct coefficients needed to balance the equation are 4, 3, and 2.

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• 29.

### What is balanced a chemical equation

• A.

The number of atoms of each element that is the same on both sides.

• B.

The weight of the elements is the same when added

• C.

They sit flat on a table

• D.

Equal all around the liquid

A. The number of atoms of each element that is the same on both sides.
Explanation
A balanced chemical equation means that the number of atoms of each element is the same on both sides of the equation. This is important because it follows the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. By balancing the equation, we ensure that the same number of atoms of each element are present before and after the reaction, maintaining the overall mass of the system.

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• 30.

### Scientific law is

• A.

A science law

• B.

Simplified set of rules to follow

• C.

Scientific generalizations of countless observations.

• D.

A little more than a hypothesis

C. Scientific generalizations of countless observations.
Explanation
Scientific laws are statements that summarize patterns or relationships observed in nature, based on extensive and repeated observations. These laws are derived from countless observations and experiments, making them reliable and widely applicable. They describe how the natural world behaves under specific conditions and are considered fundamental principles in scientific understanding. Unlike hypotheses, which are tentative explanations, scientific laws are well-established and have stood the test of time. Therefore, the answer "scientific generalizations of countless observations" accurately describes what scientific laws are.

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• 31.

### The first step you should take in balancing a chemical equation is to do an ___________

Atom / Element Inventory
Explanation
The first step in balancing a chemical equation is to do an atom/element inventory. This involves identifying all the atoms and elements present in the reactants and products of the equation. By doing an inventory, you can determine if the equation is balanced or if there are any discrepancies in the number of atoms on each side. This step is crucial as it provides a clear understanding of the elements involved and their quantities, which is necessary for balancing the equation correctly.

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• 32.

### ________________ is the atomic weights of elements can be used to find the mass of one mole of any substance.

Molar mass
Explanation
Molar mass refers to the atomic weights of elements being used to find the mass of one mole of any substance. It is a calculation that allows us to determine the mass of a substance in grams by adding up the atomic masses of each element in the compound. This concept is crucial in chemistry as it helps in various calculations, such as determining the amount of a substance needed for a reaction or understanding the composition of a compound.

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• 33.

### In Chemistry Knowing the mass of one unit enables us to count by_______________

weighing/weight
Explanation
Knowing the mass of one unit enables us to count by weighing or using weight as a measurement. By determining the mass of a single unit, we can then use that information to measure and count larger quantities of the substance by weighing them. This is a fundamental concept in chemistry, as it allows scientists to accurately determine the amount of a substance present in a sample.

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• 34.

### The number 6.02 x 10^23 represents ______________________

Explanation
The number 6.02 x 10^23 represents Avogadro's Number, which is a fundamental constant in chemistry. It is the number of particles (atoms, molecules, or ions) in one mole of a substance. A mole is a unit used to measure the amount of a substance, and Avogadro's Number allows us to relate the mass of a substance to the number of particles it contains. This number is significant in various calculations and conversions in chemistry, making it an essential concept in the field.

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• 35.

### The percent of mass by which each material found in an item is called the________________________

Percent composition
Explanation
The percent of mass by which each material found in an item is called the percent composition. This term refers to the relative amount of each element or compound present in a substance, expressed as a percentage of the total mass. It is a useful concept in chemistry to understand the composition of a substance and determine its properties and behavior.

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• 36.

### An approach that aims to eliminate pollution in industrial settings is called __________________ Back to top