87 how many cl atoms are in 3cacl₂?
a. 3
b. 6
c. 9
d. 12

88. which reaction is decomposition?
a. 2h₂ + o₂ → 2h₂o
b. caco₃ → cao + co₂
c. zn + hcl → zncl₂ + h₂
d. na + cl₂ → nacl

89. why can subscripts never be changed?
a. they change element identity
b. they change coefficients
c. they change charge
d. they change mass

90. which is a synthesis reaction?
a. 2h₂o → 2h₂ + o₂
b. 2na + cl₂ → 2nacl
c. zn + cuso₄ → znso₄ + cu
d. hcl + naoh → nacl + h₂o

91. which is single replacement?
a. 2na + cl₂ → 2nacl
b. 2h₂o → 2h₂ + o₂
c. zn + cuso₄ → znso₄ + cu
d. agno₃ + nacl → agcl + nano₃

92. which is double replacement?
a. 2h₂ + o₂ → 2h₂o
b. zn + hcl → zncl₂ + h₂
c. agno₃ + nacl → agcl + nano₃
d. caco₃ → cao + co₂

93. which side contains products?
a. left
b. right
c. top
d. bottom

94. what must be equal on both sides of a balanced equation?
a. mass
b. atoms
c. energy
d. volume

95. which compound is covalent?
a. nacl
b. mgo
c. co₂
d. cacl₂

96. which compound is ionic?
a. o₂
b. co₂
c. h₂o
d. nacl

97. which is a physical change?
a. burning
b. rusting
c. melting
d. reacting

98. glass resists chemical change because it has —
a. weak bonds
b. strong bonds
c. low mass
d. low density

99. why must equations be balanced?
a. to increase energy
b. to conserve mass
c. to create matter
d. to change atoms

100. why is conservation of mass important?
a. matter disappears
b. matter is created
c. atoms rearrange but are not destroyed
d. energy is lost

Question

87 how many cl atoms are in 3cacl₂?
a. 3
b. 6
c. 9
d. 12

88. which reaction is decomposition?
a. 2h₂ + o₂ → 2h₂o
b. caco₃ → cao + co₂
c. zn + hcl → zncl₂ + h₂
d. na + cl₂ → nacl

89. why can subscripts never be changed?
a. they change element identity
b. they change coefficients
c. they change charge
d. they change mass

90. which is a synthesis reaction?
a. 2h₂o → 2h₂ + o₂
b. 2na + cl₂ → 2nacl
c. zn + cuso₄ → znso₄ + cu
d. hcl + naoh → nacl + h₂o

91. which is single replacement?
a. 2na + cl₂ → 2nacl
b. 2h₂o → 2h₂ + o₂
c. zn + cuso₄ → znso₄ + cu
d. agno₃ + nacl → agcl + nano₃

92. which is double replacement?
a. 2h₂ + o₂ → 2h₂o
b. zn + hcl → zncl₂ + h₂
c. agno₃ + nacl → agcl + nano₃
d. caco₃ → cao + co₂

93. which side contains products?
a. left
b. right
c. top
d. bottom

94. what must be equal on both sides of a balanced equation?
a. mass
b. atoms
c. energy
d. volume

95. which compound is covalent?
a. nacl
b. mgo
c. co₂
d. cacl₂

96. which compound is ionic?
a. o₂
b. co₂
c. h₂o
d. nacl

97. which is a physical change?
a. burning
b. rusting
c. melting
d. reacting

98. glass resists chemical change because it has —
a. weak bonds
b. strong bonds
c. low mass
d. low density

99. why must equations be balanced?
a. to increase energy
b. to conserve mass
c. to create matter
d. to change atoms

100. why is conservation of mass important?
a. matter disappears
b. matter is created
c. atoms rearrange but are not destroyed
d. energy is lost

Accepted Answer

### Question 87: How many Cl atoms are in $ 3\text{CaCl}_2 $?
# Explanation:
## Step 1: Analyze the formula
In $ \text{CaCl}_2 $, the subscript of Cl is 2, meaning each $ \text{CaCl}_2 $ has 2 Cl atoms.
## Step 2: Multiply by the coefficient
The coefficient is 3, so total Cl atoms = $ 3 \times 2 = 6 $.
# Answer: B. 6

### Question 88: Which reaction is decomposition?
# Brief Explanations:
A decomposition reaction breaks a compound into simpler substances. Option A is synthesis (combining $ \text{H}_2 $ and $ \text{O}_2 $), C is single replacement (Zn replaces H), D is synthesis (Na and $ \text{Cl}_2 $ combine). Option B: $ \text{CaCO}_3
ightarrow \text{CaO} + \text{CO}_2 $ breaks $ \text{CaCO}_3 $ into two simpler compounds.
# Answer: B. $ \text{CaCO}_3
ightarrow \text{CaO} + \text{CO}_2 $

### Question 89: Why can subscripts never be changed?
# Brief Explanations:
Subscripts in a chemical formula represent the ratio of atoms in a compound. Changing subscripts would change the compound's identity (e.g., $ \text{H}_2\text{O} $ vs $ \text{H}_2\text{O}_2 $ are different). Option B is incorrect (subscripts don’t affect coefficients), C is about charge (not subscripts), D is incorrect (subscripts relate to atom ratio, not mass directly).
# Answer: A. They change element identity

### Question 90: Which is a synthesis reaction?
# Brief Explanations:
Synthesis reactions combine substances into a single compound. Option A is decomposition (breaks $ \text{H}_2\text{O} $), C is single replacement (Zn replaces Cu), D is neutralization (acid - base). Option B: $ 2\text{Na} + \text{Cl}_2
ightarrow 2\text{NaCl} $ combines Na and $ \text{Cl}_2 $ into $ \text{NaCl} $.
# Answer: B. $ 2\text{Na} + \text{Cl}_2
ightarrow 2\text{NaCl} $

### Question 91: Which is single replacement?
# Brief Explanations:
Single replacement involves one element replacing another in a compound. Option A is synthesis, B is decomposition, D is double replacement (ions swap). Option C: $ \text{Zn} + \text{CuSO}_4
ightarrow \text{ZnSO}_4 + \text{Cu} $ has Zn replacing Cu in $ \text{CuSO}_4 $.
# Answer: C. $ \text{Zn} + \text{CuSO}_4
ightarrow \text{ZnSO}_4 + \text{Cu} $

### Question 92: Which is double replacement?
# Brief Explanations:
Double replacement reactions involve ions swapping between compounds. Option A is synthesis, B is single replacement, D is decomposition. Option C: $ \text{AgNO}_3 + \text{NaCl}
ightarrow \text{AgCl} + \text{NaNO}_3 $ has $ \text{Ag}^+ $ and $ \text{Na}^+ $ swapping with $ \text{NO}_3^- $ and $ \text{Cl}^- $.
# Answer: C. $ \text{AgNO}_3 + \text{NaCl}
ightarrow \text{AgCl} + \text{NaNO}_3 $

### Question 93: Which side contains products?
# Brief Explanations:
In a chemical equation, reactants are on the left, products (substances formed) are on the right (e.g., $ \text{Reactants}
ightarrow \text{Products} $).
# Answer: B. Right

### Question 94: What must be equal on both sides of a balanced equation?
# Brief Explanations:
A balanced chemical equation has equal numbers of each type of atom on both sides (Law of Conservation of Mass). Mass is conserved, but the question asks what is equal. Atoms (of each element) must be equal. Energy (C) and volume (D) are not conserved in the same way, and “mass” (A) is conserved because atoms are equal, but the direct equality is of atoms.
# Answer: B. Atoms

### Question 95: Which compound is covalent?
# Brief Explanations:
Covalent compounds are usually between nonmetals. Ionic compounds are between metals and nonmetals. NaCl (A), MgO (B), $ \text{CaCl}_2 $ (D) are ionic (metal - nonmetal). $ \text{CO}_2 $ (C) is between C and O (both nonmetals), so covalent.
# Answer: C. $ \text{CO}_2 $

### Question 96: Which compound is ionic?
# Brief Explanations:
Ionic compounds form between metals and nonmetals. $ \text{O}_2 $ (A) is a diatomic element, $ \text{CO}_2 $ (B) and $ \text{H}_2\text{O} $ (C) are covalent (nonmetal - nonmetal). NaCl (D) is between Na (metal) and Cl (nonmetal), so ionic.
# Answer: D. NaCl

### Question 97: Which is a physical change?
# Brief Explanations:
Physical changes don’t form new substances. Burning (A), rusting (B), and reacting (D) are chemical changes (new substances form). Melting (C) is a phase change (solid to liquid) with no new substance, so physical.
# Answer: C. Melting

### Question 98: Glass resists chemical change because it has —
# Brief Explanations:
Glass is chemically stable because its bonds (silicate structure) are strong, making it hard to break and react. Weak bonds (A) would make it reactive, low mass (C) and low density (D) don’t relate to chemical resistance.
# Answer: B. Strong bonds

### Question 99: Why must equations be balanced?
# Brief Explanations:
To follow the Law of Conservation of Mass, which states matter is neither created nor destroyed. So equations are balanced to conserve mass (B). Increasing energy (A) is incorrect, creating matter (C) violates the law, changing atoms (D) is impossible (atoms are conserved, not changed).
# Answer: B. To conserve mass

### Question 100: Why is conservation of mass important?
# Brief Explanations:
Conservation of Mass means atoms rearrange in reactions but are not destroyed (C). Matter doesn’t disappear (A) or get created (B), and energy loss (D) is a different concept (Law of Conservation of Energy).
# Answer: C. Atoms rearrange but are not destroyed

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Question 87: How many Cl atoms are in \( 3\text{CaCl}_2 \)?

Step 1: Analyze the formula

Step 2: Multiply by the coefficient

Answer:

Question 88: Which reaction is decomposition?