133. which atom has a -3 change in oxidation number during the following redox reaction?
$\text{k}_2\text{cr}_2\text{o}_7 + \text{h}_2\text{o} + \text{s} \
ightarrow \text{koh} + \text{cr}_2\text{o}_3 + \text{so}_2$
a. k
b. cr
c. o
d. s

134. in the following unbalanced reaction, which atom is reduced?
$\text{h}_2\text{o} + \text{cl}_2 + \text{so}_2 \
ightarrow \text{hcl} + \text{h}_2\text{so}_4$
a. hydrogen
b. oxygen
c. chlorine
d. sulfur

135. which of the following chemical equations represents an oxidation-reduction reaction?
a. $\text{mg(oh)}_2 + 2\text{hcl} \
ightarrow \text{mgcl}_2 + 2\text{h}_2\text{o}$
b. $\text{bicl}_3 + \text{na}_2\text{so}_4 \
ightarrow 2\text{nacl} + \text{biso}_4$
c. $\text{ch}_4 + 2\text{o}_2 \
ightarrow \text{co}_2 + 2\text{h}_2\text{o}$
d. $3\text{naoh} + \text{h}_3\text{po}_4 \
ightarrow \text{na}_3\text{po}_4 + 3\text{h}_2\text{o}$

136. which element increases its oxidation number in the following reaction?
$3\text{koh} + \text{h}_3\text{po}_4 \
ightarrow \text{k}_3\text{po}_4 + 3\text{h}_2\text{o}$
a. oxygen
b. potassium
c. phosphorus
d. no changes in oxidation number

137. which of the following chemical equations represents a redox reaction?
a. $2\text{na} + 2\text{h}_2\text{o} \
ightarrow 2\text{naoh} + \text{h}_2$
b. $\text{hcl} + \text{koh} \
ightarrow \text{kcl} + \text{h}_2\text{o}$
c. $\text{agno}_3(aq) + \text{nacl}(aq) \
ightarrow \text{nano}_3(aq) + \text{agcl}(s) + \text{h}_2\text{o}(l)$
d. $\text{fe}^{3+} + 3\text{no}_3^- + 3\text{na}^+ + 3\text{oh}^- \
ightarrow \text{fe(oh)}_3 + 3\text{na}^+ + 3\text{no}_3^-$

138. which of the following types of reactions is always a redox reaction?
a. acid-base
b. double-replacement
c. combustion
d. neutralization

139. what is the reduction half-reaction for the following unbalanced redox equation?
$\text{cr}_2\text{o}_7^{2-} + \text{nh}_4^+ \
ightarrow \text{cr}_2\text{o}_3 + \text{n}_2$
a. $\text{cr}_2\text{o}_3 \
ightarrow \text{cr}_2\text{o}_7^{2-}$
b. $\text{cr}_2\text{o}_7^{2-} \
ightarrow \text{cr}_2\text{o}_3$
c. $\text{nh}_4^+ \
ightarrow \text{n}_2$
d. $\text{n}_2 \
ightarrow \text{nh}_4^+$

Question

133. which atom has a -3 change in oxidation number during the following redox reaction?
$\text{k}_2\text{cr}_2\text{o}_7 + \text{h}_2\text{o} + \text{s} \
ightarrow \text{koh} + \text{cr}_2\text{o}_3 + \text{so}_2$
a. k
b. cr
c. o
d. s

134. in the following unbalanced reaction, which atom is reduced?
$\text{h}_2\text{o} + \text{cl}_2 + \text{so}_2 \
ightarrow \text{hcl} + \text{h}_2\text{so}_4$
a. hydrogen
b. oxygen
c. chlorine
d. sulfur

135. which of the following chemical equations represents an oxidation-reduction reaction?
a. $\text{mg(oh)}_2 + 2\text{hcl} \
ightarrow \text{mgcl}_2 + 2\text{h}_2\text{o}$
b. $\text{bicl}_3 + \text{na}_2\text{so}_4 \
ightarrow 2\text{nacl} + \text{biso}_4$
c. $\text{ch}_4 + 2\text{o}_2 \
ightarrow \text{co}_2 + 2\text{h}_2\text{o}$
d. $3\text{naoh} + \text{h}_3\text{po}_4 \
ightarrow \text{na}_3\text{po}_4 + 3\text{h}_2\text{o}$

136. which element increases its oxidation number in the following reaction?
$3\text{koh} + \text{h}_3\text{po}_4 \
ightarrow \text{k}_3\text{po}_4 + 3\text{h}_2\text{o}$
a. oxygen
b. potassium
c. phosphorus
d. no changes in oxidation number

137. which of the following chemical equations represents a redox reaction?
a. $2\text{na} + 2\text{h}_2\text{o} \
ightarrow 2\text{naoh} + \text{h}_2$
b. $\text{hcl} + \text{koh} \
ightarrow \text{kcl} + \text{h}_2\text{o}$
c. $\text{agno}_3(aq) + \text{nacl}(aq) \
ightarrow \text{nano}_3(aq) + \text{agcl}(s) + \text{h}_2\text{o}(l)$
d. $\text{fe}^{3+} + 3\text{no}_3^- + 3\text{na}^+ + 3\text{oh}^- \
ightarrow \text{fe(oh)}_3 + 3\text{na}^+ + 3\text{no}_3^-$

138. which of the following types of reactions is always a redox reaction?
a. acid-base
b. double-replacement
c. combustion
d. neutralization

139. what is the reduction half-reaction for the following unbalanced redox equation?
$\text{cr}_2\text{o}_7^{2-} + \text{nh}_4^+ \
ightarrow \text{cr}_2\text{o}_3 + \text{n}_2$
a. $\text{cr}_2\text{o}_3 \
ightarrow \text{cr}_2\text{o}_7^{2-}$
b. $\text{cr}_2\text{o}_7^{2-} \
ightarrow \text{cr}_2\text{o}_3$
c. $\text{nh}_4^+ \
ightarrow \text{n}_2$
d. $\text{n}_2 \
ightarrow \text{nh}_4^+$

Accepted Answer

{ "quality": "clear", "question_count": 7, "skills_matched": [ "step_cot", "multiple_choice_formatter", "explain_then_answer", "tutor", "mastery_adaptive_brevity" ], "needs_drawing": false, "concepts_used": [ "Oxidation Numbers", "Redox Rules", "Half-Reaction Method" ], "new_concepts": [], "current_concepts": [ "Oxidation Numbers", "Redox Rules", "Half-Reaction Method", "Redox Balancing" ] } ## Determine oxidation state changes for Question 133 Using the *Oxidation Numbers* and *Redox Rules* knowledge points $$ \begin{aligned} &\text{In } \text{K}_2\text{Cr}_2\text{O}_7: \text{K} = +1, \text{O} = -2 \implies 2(+1) + 2(\text{Cr}) + 7(-2) = 0 \implies \text{Cr} = +6\ &\text{In } \text{Cr}_2\text{O}_3: \text{O} = -2 \implies 2(\text{Cr}) + 3(-2) = 0 \implies \text{Cr} = +3\ &\text{Change for Cr}: +3 - (+6) = -3 \end{aligned} $$ ## Identify the reduced atom in Question 134 Using the *Oxidation Numbers* and *Redox Rules* knowledge points $$ \begin{aligned} &\text{In } \text{Cl}_2 \text{ (elemental form)}: \text{Cl} = 0\ &\text{In } \text{HCl}: \text{H} = +1 \implies \text{Cl} = -1\ &\text{Since the oxidation number of chlorine decreases from } 0 \text{ to } -1\text{, chlorine is reduced.} \end{aligned} $$ ## Identify the redox reaction in Question 135 Using the *Oxidation Numbers* and *Redox Rules* knowledge points $$ \begin{aligned} &\text{In reaction (c): } \text{CH}_4 + 2\text{O}_2 ightarrow \text{CO}_2 + 2\text{H}_2\text{O}\ &\text{Reactants: C in } \text{CH}_4 = -4, \text{O in } \text{O}_2 = 0\ &\text{Products: C in } \text{CO}_2 = +4, \text{O in } \text{CO}_2 \text{ and } \text{H}_2\text{O} = -2\ &\text{Since oxidation numbers change, this is a redox reaction.} \end{aligned} $$ ## Analyze oxidation number changes in Question 136 Using the *Oxidation Numbers* and *Redox Rules* knowledge points $$ \begin{aligned} &\text{Reactants: } \text{K} = +1, \text{O} = -2, \text{H} = +1 \text{ (in KOH and } \text{H}_3\text{PO}_4\text{)}, \text{P} = +5 \text{ (in } \text{H}_3\text{PO}_4\text{)}\ &\text{Products: } \text{K} = +1, \text{P} = +5, \text{O} = -2 \text{ (in } \text{K}_3\text{PO}_4\text{)}, \text{H} = +1, \text{O} = -2 \text{ (in } \text{H}_2\text{O}\text{)}\ &\text{No elements change their oxidation numbers during this acid-base neutralization reaction.} \end{aligned} $$ ## Identify the redox reaction in Question 137 Using the *Oxidation Numbers* and *Redox Rules* knowledge points $$ \begin{aligned} &\text{In reaction (a): } 2\text{Na} + 2\text{H}_2\text{O} ightarrow 2\text{NaOH} + \text{H}_2\ &\text{Reactants: Na} = 0, \text{H in } \text{H}_2\text{O} = +1\ &\text{Products: Na in NaOH} = +1, \text{H in } \text{H}_2 = 0\ &\text{Since oxidation numbers change, this is a redox reaction.} \end{aligned} $$ ## Determine the reaction type that is always redox in Question 138 Using the *Oxidation Numbers* knowledge point $$ \begin{aligned} &\text{Combustion always involves a substance reacting with elemental oxygen } (\text{O}_2, \text{ oxidation state } 0)\ &\text{to form compounds where oxygen has an oxidation state of } -2.\ &\text{Therefore, combustion is always a redox reaction.} \end{aligned} $$ ## Identify the reduction half-reaction in Question 139 Using the *Half-Reaction Method* and *Oxidation Numbers* knowledge points $$ \begin{aligned} &\text{In } \text{Cr}_2\text{O}_7^{2-}: \text{Cr} = +6\ &\text{In } \text{Cr}_2\text{O}_3: \text{Cr} = +3\ &\text{Reduction is the decrease in oxidation state: } \text{Cr}_2\text{O}_7^{2-} ightarrow \text{Cr}_2\text{O}_3 \end{aligned} $$ ## Question 133 a. K

b. Cr

c. O

d. S ## Question 134 a. hydrogen

b. oxygen c. chlorine d. sulfur ## Question 135 a. Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

b. BiCl₂ + Na₂SO₄ → 2NaCl + BiSO₄

c. CH₄ + 2O₂ → CO₂ + 2H₂O

d. 3NaOH + H₃PO₄ → Na₃PO₄ + 3H₂O ## Question 136 a. oxygen

b. potassium

c. phosphorus

d. no changes in oxidation number ## Question 137 a. 2Na + 2H₂O → 2NaOH + H₂

b. HCl + KOH → KCl + H₂O

c. AgNO₃(aq) + NaCl(aq) → NaNO₃(aq) + AgCl(s) + H₂O(l)

d. Fe³⁺ + 3NO₃⁻ + 3Na⁺ + 3OH⁻ → Fe(OH)₃ + 3Na⁺ + 3NO₃⁻ ## Question 138 a. acid-base

b. double-replacement

c. combustion

d. neutralization ## Question 139 a. Cr₂O₃ → Cr₂O₇²⁻

b. Cr₂O₇²⁻ → Cr₂O₃

c. NH₄⁺ → N₂

d. N₂ → NH₄⁺

{ "subject": "Natural Science", "question_type": "Multi-part", "knowledge_point": [ "Natural Science", "Chemistry", "Redox Reactions" ] }

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Determine oxidation state changes for Question 133

Identify the reduced atom in Question 134

Identify the redox reaction in Question 135

Analyze oxidation number changes in Question 136

Identify the redox reaction in Question 137

Determine the reaction type that is always redox in Question 138

Identify the reduction half-reaction in Question 139

Answer:

Question 133

Question 134

Question 135

Question 136

Question 137

Question 138

Question 139