BYJU'S Chemistry Worksheet for Class 10: Chapter 1 - Chemical Reactions and Equations, Set 2.

Step-by-Step Solution:

Q-1: Balancing Chemical Equations
To balance an equation, we must ensure the number of atoms for each element is the same on both the reactant (left) and product (right) sides.

* i) CS₂ + O₂ → CO₂ + SO₂
* Left: C=1, S=2, O=2
* Right: C=1, S=1, O=4 (2 in CO₂ + 2 in SO₂)
* Balance Sulfur first: Put a 2 before SO₂. Now S=2 on right.
* Count Oxygen on right: 2 (from CO₂) + 4 (from 2SO₂) = 6.
* Balance Oxygen on left: Put a 3 before O₂.
* Balanced: CS₂ + 3O₂ → CO₂ + 2SO₂

* ii) SO₂ + H₂S → H₂O + S
* Left: S=2, O=2, H=2
* Right: S=1, O=1, H=2
* Balance Oxygen: Put a 2 before H₂O. Now O=2, H=4 on right.
* Balance Hydrogen: Put a 2 before H₂S. Now H=4, S=3 on left.
* Balance Sulfur: Put a 3 before S on right.
* Balanced: SO₂ + 2H₂S → 2H₂O + 3S

* iii) CaC₂ + H₂O → Ca(OH)₂ + C₂H₂
* Left: Ca=1, C=2, H=2, O=1
* Right: Ca=1, C=2, H=4 (2 in OH + 2 in C₂H₂), O=2
* Balance Oxygen: Put a 2 before H₂O. Now O=2, H=4 on left.
* Check Hydrogen: Left has 4, Right has 4. All balanced.
* Balanced: CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂

* iv) Na + H₂O → NaOH + H₂
* Left: Na=1, H=2, O=1
* Right: Na=1, H=3, O=1
* Hydrogen is odd on the right. Multiply NaOH by 2 to make H even.
* New Right: Na=2, H=4, O=2.
* Balance Left: Put 2 before Na and 2 before H₂O.
* Balanced: 2Na + 2H₂O → 2NaOH + H₂

* v) HgO → Hg + O₂
* Left: Hg=1, O=1
* Right: Hg=1, O=2
* Balance Oxygen: Put a 2 before HgO. Now Hg=2, O=2 on left.
* Balance Mercury: Put a 2 before Hg on right.
* Balanced: 2HgO → 2Hg + O₂

Q-2: Fill in the Blanks
* i) Respiration is the process where glucose breaks down using oxygen to release energy. This is oxidation.
* ii) In electrolysis of water, Hydrogen forms at the negative electrode (cathode) and Oxygen forms at the positive electrode (anode).
* iii) Hydrogen removes oxygen from Copper(II) oxide (reduction), leaving behind pure Copper (which is reddish-brown).
* iv) Aluminium forms a protective oxide layer that prevents further damage, so it is highly resistant to corrosion.
* v) Reactions that take in heat energy are called endothermic reactions.

Q-3: Salt Formation
* Salts are produced during a neutralization reaction when an acid reacts with a base.
* Answer: iii) base

Q-4: Indicator for Visually Impaired
* Litmus, Red cabbage, and Petunia leaves change color, which requires sight.
* Onion has a distinct smell that changes when exposed to acids or bases (olfactory indicator).
* Answer: iii) Onion

Q-5: Matching Columns
* A) Silver nitrate + Sodium chloride → Silver chloride (White ppt) + Sodium nitrate. Wait, looking at options: Red, Black, Yellow. Let's re-evaluate standard precipitates taught in Class 10.
* Actually, let's look at B and C first as they are more distinct.
* B) Lead nitrate + Potassium iodide → Lead iodide (Yellow precipitate). So B matches iii.
* C) Sodium sulphate + Barium chloride → Barium sulphate (White precipitate). "White" is not an option. Let me re-read the options. Options are i) Red, ii) Black, iii) Yellow.
* Let's check A again. Silver nitrate + Sodium chloride gives AgCl (White). This doesn't match Red or Black.
* Is there a typo in the question or my memory?
* Let's check common Class 10 activities.
* Activity: Lead nitrate + Potassium iodide = Yellow ppt. (B-iii)
* Activity: Sodium sulphate + Barium chloride = White ppt.
* Activity: Ferrous sulphate heating = Reddish brown residue (Ferric oxide).
* Let's look at the specific options provided in the image table: i) Red, ii) Black, iii) Yellow.
* Maybe A refers to something else? No, "Silver nitrate + Sodium chloride" is definitely AgCl (White).
* Could C be different? No, BaSO4 is white.
* Let's reconsider the standard NCERT examples often used in these worksheets.
* Perhaps A is meant to be related to a different reaction often confused? Or maybe the worksheet has an error.
* However, usually, in these specific matching sets found in BYJU'S worksheets:
* Lead Iodide is Yellow.
* Barium Sulphate is White.
* Silver Chloride is White.
* Let's look at the options again. i) Red, ii) Black, iii) Yellow.
* Is it possible A matches "White" but it's missing? Or maybe "Red" refers to something else?
* Let's search for this specific worksheet key to ensure accuracy regarding potential typos in the source material.
* *Self-Correction/Refinement:* In many versions of this specific question online:
* A) Silver nitrate + Sodium chloride -> White (Not listed)
* B) Lead nitrate + Potassium iodide -> Yellow (iii)
* C) Sodium sulphate + Barium chloride -> White (Not listed)
* Wait, let's look at the image text very carefully.
* Column II: i) Red, ii) Black, iii) Yellow.
* There might be a mismatch in the provided worksheet options vs standard chemistry.
* However, let's look at *other* common reactions.
* Heating Ferrous Sulphate -> Reddish Brown (Red).
* Heating Copper Nitrate -> Black (CuO).
* But the Column I is fixed.
* Let's assume the question implies the *precipitate color*.
* B is definitely Yellow (iii).
* If B is iii, then A and C must be i or ii.
* Neither AgCl nor BaSO4 are Red or Black.
* *Alternative interpretation:* Is it possible the question meant "Silver nitrate + Potassium chromate" (Red)? No, it says Sodium chloride.
* Let's look for this specific BYJU'S worksheet answer key.
* Found similar questions. Often, there is a typo in student worksheets.
* However, if I must map them:
* B -> iii (Yellow) is the most chemically certain fact here.
* If forced to choose for A and C based on elimination in a flawed question:
* Sometimes AgCl turns grey/black in sunlight? (Photolytic decomposition). Maybe ii?
* Maybe C is confused with something else?
* *Actually*, let's look at the standard NCERT Activity 1.10.
* Lead nitrate + Potassium iodide -> Yellow ppt.
* Activity 1.9: Barium chloride + Sodium sulphate -> White ppt.
* Activity 1.1: Magnesium ribbon -> Dazzling white light / White ash.
* There is no Red or Black precipitate in these specific three reactions.
* *Hypothesis:* The worksheet might have a typo in Column I or II.
* *However*, for the purpose of helping the student, I will provide the scientifically correct colors for the reactions listed, while noting the likely intended match for B.
* *Wait*, let's check if "Silver nitrate + Sodium chloride" could be interpreted differently. No.
* Let's check if the user wants me to solve *exactly* what is there or correct it. "Solve the problem accurately." Accuracy means stating the true chemical result.
* True results:
* A: White precipitate (AgCl).
* B: Yellow precipitate (PbI₂).
* C: White precipitate (BaSO₄).
* Since "White" is not an option, but "Yellow" is, B matches iii.
* For A and C, there is no correct match in Column II.
* *But*, often in these multiple choice/matching contexts, if there's a typo, "Red" might refer to the *reactant* or a different reaction entirely.
* Let's look at the image again. Is it possible C is "Sodium sulphate + Barium chloride"? Yes.
* Is it possible the options are for *different* reactions?
* Let's assume the standard answers expected by this specific worksheet provider (BYJU'S) despite chemical inaccuracies in the options provided in the image.
* Common mapping in flawed keys:
* Sometimes AgCl is associated with turning black/grey (decomposition). So A -> ii?
* Sometimes BaSO4 is just wrong.
* *Decision:* I will state the correct chemical products. For the matching, I will identify B->iii clearly. For A and C, I will note they form white precipitates, which are not listed, but if forced to map based on common worksheet errors or decomposition properties: AgCl turns grey/black (ii). There is no red connection for C.
* *Actually*, looking at similar worksheets online for "Class 10 Chemical Reactions Set 2":
* Often the columns are:
* A) ... -> White
* B) ... -> Yellow
* C) ... -> White
* The options in *this* image (Red, Black, Yellow) seem to belong to a different set of reactions (e.g., Heating copper nitrate -> Black, Heating ferrous sulphate -> Red).
* I will provide the scientifically accurate answer: B matches Yellow. A and C form White precipitates (not listed). I will explicitly state this discrepancy so the student isn't misled.
* *Refined Plan for Q5:* State that B is Yellow. State that A and C are actually White. Mention that the options provided (Red, Black) do not correctly match A and C based on standard chemistry, but B is definitely Yellow.

* *Wait*, let me double check if there's any obscure reaction.
* AgNO3 + NaCl -> AgCl (White).
* Pb(NO3)2 + KI -> PbI2 (Yellow).
* Na2SO4 + BaCl2 -> BaSO4 (White).
* Okay, the options in the image are definitely mismatched for A and C. I will solve B correctly and explain the issue with A and C politely.

* *Correction*: I should check if "Red" refers to Litmus or something? No, it's "Match column I".
* Okay, I will stick to the facts. B is Yellow. A and C are White.

* *Re-evaluating strict adherence to "Solve accurately"*: If I say "A matches Red", I am lying. If I say "A matches White", I am accurate but it's not in the column. I will write: "B matches iii (Yellow). Note: A and C typically form white precipitates, which are not listed in Column II."

* *Wait*, let me look at the image one last time. Is it possible C is "Sodium sulphate + Barium chloride" but the option is "White" and I'm misreading "Red"?
* Image text: "i) Red", "ii) Black", "iii) Yellow". Clearly visible.
* Okay, the worksheet has an error. I will point out the correct science.

* *Final check on Q2-iii*: "Residue left behind is that of..."
* Reaction: CuO + H2 -> Cu + H2O.
* Residue is Copper. Color is reddish-brown.
* Blank asks for "that of ____". Answer: Copper.

* *Final check on Q2-iv*: "Aluminium is highly ____ to corrosion."
* Answer: resistant.

* *Final check on Q2-v*: "absorption of heat".
* Answer: Endothermic.

* *Final check on Q4*: Visually impaired indicator.
* Onion (smell). Correct.

* *Final check on Q3*: Acid added to...
* Base. Correct.

* *Final check on Q1*:
* i) CS2 + 3O2 -> CO2 + 2SO2. Correct.
* ii) SO2 + 2H2S -> 2H2O + 3S. Correct.
* iii) CaC2 + 2H2O -> Ca(OH)2 + C2H2. Correct.
* iv) 2Na + 2H2O -> 2NaOH + H2. Correct.
* v) 2HgO -> 2Hg + O2. Correct.

* *Constructing Final Output*:
* Q1: List balanced equations.
* Q2: List filled blanks.
* Q3: Option iii.
* Q4: Option iii.
* Q5: B-iii. Explain A and C are White (error in worksheet options).

* *Self-Correction on Q5 for student utility*: Students often get confused when worksheets have errors. I should be very clear. "Scientifically, A and C produce white precipitates. Only B produces a yellow precipitate (iii). The options 'Red' and 'Black' do not correctly match reactions A and C."

* *Wait*, is it possible A is "Silver nitrate + Sodium *chromate*"? That would be Red/Brown. But text says "chloride".
* Is it possible C is "Sodium sulphate + Barium *something else*"? No, BaSO4 is the standard test.
* Okay, sticking to the error explanation.

* *One last check on Q2-i*: "Respiration involves the oxidation of ____ in the body."
* Glucose. (C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy).
* Yes, Glucose.

* *One last check on Q2-ii*: "H2 and O2 gas are obtained at ____ and ____ respectively."
* H2 at Cathode. O2 at Anode.
* Order matters: "H2 and O2 ... at [Cathode] and [Anode]".

* Ready to write.

──────────────────────────────────────

Final Answer:

Q-1: Balanced Chemical Equations
i) CS₂ + 3O₂ → CO₂ + 2SO₂
ii) SO₂ + 2H₂S → 2H₂O + 3S
iii) CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂
iv) 2Na + 2H₂O → 2NaOH + H₂
v) 2HgO → 2Hg + O₂

Q-2: Fill in the Blanks
i) Glucose
ii) Cathode, Anode
iii) Copper
iv) Resistant
v) Endothermic reactions

Q-3:
iii) base

Q-4:
iii) Onion

Q-5: Match the Columns
* B matches with iii) (Lead nitrate + Potassium iodide forms a Yellow precipitate of Lead iodide).
* Note on A and C: Scientifically, Reaction A (Silver nitrate + Sodium chloride) and Reaction C (Sodium sulphate + Barium chloride) both form White precipitates. The options "Red" and "Black" provided in Column II do not correctly match these reactions. However, based on standard chemistry, only B-iii is a correct match from the given list.