MCQ
Chemistry MCQ - Practice Questions with Answers
Solve 10 Chemistry questions for RAS/RPSC preparation.
Practice questions
Q1A village first-aid chart lists four pairings: 1. Excess acid in the stomach → Mg(OH)₂ 2. Honey-bee sting → NaHCO₃ 3. Crop soil that is too acidic → CaO 4. Crop soil that is too acidic → dilute HCl Let P be how many of these pairings are chemically appropriate. Let H be the number of hydrogen atoms in one formula unit of the stomach antacid written in pairing 1. Which value equals 10P + H?
Mg(OH)₂ is a mild base used as an antacid, so pairing 1 is appropriate and that formula unit holds H = 2 hydrogen atoms. Baking soda NaHCO₃ soothes a bee-sting acid, so pairing 2 is appropriate. Too-acidic soil is treated with bases such as quick lime CaO, so pairing 3 is appropriate, while dilute HCl would worsen acidity, so pairing 4 is not. Thus P = 3 and 10P + H = 30 + 2 = 32.
Q2A materials clerk files four polymer cards. Each card lists polymer → claimed polymerisation class → by-product note: Card 1 — Nylon-6,6 → condensation → small molecules such as water eliminated Card 2 — Polythene → addition → no small-molecule by-product Card 3 — PVC → condensation → HCl released as a small-molecule by-product Card 4 — Bakelite → condensation → small molecules eliminated Exactly one card is factually wrong in its class/by-product pairing. Let F be that card's number. Let R be how many of the four cards correctly classify their polymer. Which value equals R² + F?
Nylon-6,6 and bakelite are condensation polymers that eliminate small molecules; polythene and PVC are addition polymers with no small-molecule by-product. Card 3 alone is wrong (PVC is addition, not condensation with HCl release). Cards 1, 2 and 4 are correct, so R=3 and F=3. Therefore R²+F=12.
Q3A brine cell is run and one electrode gas is absorbed on dry slaked lime to give a white solid that municipal plants dose into drinking-water tanks to free the water from germs. Four lab slips record (electrode gas ; solid formula ; Cl atoms counted in one formula unit of that solid): P. H₂ ; Ca(ClO)₂ ; 2 Q. Cl₂ ; Ca(ClO)₂ ; 1 R. Cl₂ ; Ca(ClO)₂ ; 2 S. Cl₂ ; Na₂CO₃·10H₂O ; 0 Exactly one slip is correct in all three fields. Let N be the Cl-atom count written on that slip. Let Z be the atomic number of the halogen in the electrode gas named on that slip. What is Z + N?
Brine electrolysis liberates Cl₂ at the anode. Chlorine on dry slaked lime yields bleaching powder written Ca(ClO)₂, which is dosed so drinking water is free from germs. Slip P wrongly names H₂; slip Q undercounts Cl atoms as 1; slip S swaps in washing soda. Only slip R is fully correct, so N = 2. Chlorine’s atomic number is Z = 17, hence Z + N = 19.
Q4Match List-I with List-II and select the correct code. List-I (Need / process) 1. Heating the sodium salt of a carboxylic acid so that a hydrocarbon is obtained 2. Softening water that shows permanent hardness 3. Making drinking water free from germs 4. Releasing carbon dioxide in dough when a kitchen salt is heated List-II (Substance / mixture) W. Ca(ClO)₂ X. NaHCO₃ Y. NaOH and CaO Z. Na₂CO₃·10H₂O
Decarboxylation of a sodium carboxylate uses the NaOH+CaO mixture (Y). Permanent hardness is removed by washing soda Na₂CO₃·10H₂O (Z). Germ-free drinking water uses bleaching powder Ca(ClO)₂ (W). Heated NaHCO₃ (X) releases CO₂ that raises dough. Hence 1-Y, 2-Z, 3-W, 4-X → B.
Q5A clinic board lists four remedy → nature → gastric-role claims for excess stomach HCl after a heavy meal: 1. Baking soda NaHCO₃ → mild base → permanently locks stomach pH far above neutrality so acid production stops forever 2. Milk of magnesia Mg(OH)₂ → mild insoluble hydroxide → neutralises excess HCl without forcing the stomach strongly alkaline 3. Washing soda Na₂CO₃·10H₂O → strong laundry alkali → preferred oral antacid over magnesium hydroxide for heartburn 4. Common salt NaCl → neutral salt → neutralises excess gastric HCl by common-ion suppression Exactly one claim-row is chemically sound for everyday antacid use. Let R be that row’s number. Let O be the number of oxygen atoms in Mg(OH)₂. What is 10R + O?
Excess gastric HCl needs a mild base. Milk of magnesia Mg(OH)₂ is a mild insoluble hydroxide that neutralises excess acid without driving the stomach strongly alkaline, so only row 2 is fully sound and R=2. Mg(OH)₂ contains two oxygen atoms, so O=2 and 10R+O=22. Row 1 overstates baking soda’s lasting pH lock; washing soda is not the preferred oral heartburn antacid; NaCl does not neutralise HCl by common-ion suppression.
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6A materials clerk files four polymer cards. Each card lists polymer → claimed polymerisation class: 1. Nylon-6,6 → condensation 2. Polythene → addition 3. Terylene → addition 4. PVC → addition Let C be how many cards state the correct class. Let W be the serial number of the single card that states the wrong class. Which value equals C × W?
7A wiring consultant marks exactly these four assertions about copper alloys: 1. Brass contains copper with zinc and is a poorer electrical conductor than pure copper. 2. Bronze contains copper with tin and is a better electrical conductor than pure copper. 3. Brass contains copper with tin and is preferred over pure copper for house wiring. 4. Bronze contains copper with tin and is a poorer electrical conductor than pure copper. Let T be how many of these four assertions are entirely correct. Let Z be the atomic number of zinc and S the atomic number of tin. Which value equals T × S − Z?
8A dual-duty municipal store must issue one solid credited in textbooks with bleaching cotton and linen in textile work and with disinfecting drinking water to make it potable. Four requisition slips are under review: Slip 1 — CaOCl₂ Slip 2 — Na₂CO₃·10H₂O Slip 3 — NaHCO₃ Slip 4 — Ca(OH)₂ Exactly one slip names the correct solid for both duties. Let K be that slip’s number. Let L be the number of distinct element symbols in the formula written on that slip. What is 10K + L?
9A metals desk records four alloy dossiers: Dossier 1 — Brass = Cu+Zn; electrical conductivity higher than pure copper Dossier 2 — Bronze = Cu+Sn; electrical conductivity lower than pure copper Dossier 3 — Brass = Cu+Sn; preferred for house wiring over pure copper Dossier 4 — Bronze = Cu+Zn; electrical conductivity lower than pure copper Let N be how many dossiers are entirely correct. Let Z be the atomic number of zinc and S the atomic number of tin. Which value equals S − Z + 10N?
10A school store keeps four sealed jars for an organic practical: Jar 1 — CaOCl₂ Jar 2 — Na₂CO₃·10H₂O Jar 3 — intimate mixture of NaOH and CaO Jar 4 — intimate mixture of CaO and Ca(OH)₂ Only one jar, when strongly heated with dry sodium ethanoate, liberates a colourless hydrocarbon gas that is the first member of the alkane series. Let M be the molar mass (in g mol⁻¹) of that gas. Let O be the total number of oxygen atoms in the two simplest chemical formulas written once each on the successful jar. What is M + O?