तुरंत तैयार कर लो इन सवालों के जवाब, हर साल पूछे जाते हैं ये 12वीं की Chemistry बोर्ड परीक्षा में

12वीं के तीन विषय Physics, Chemistry और Biology में अगर तुलना की जाये तो यह कहना गलत नहीं होगा की कक्षा Chemistry का सिलेबस सबसे ज़्यादा होता है l इसलिए Chemistry जैसे विषय के लिए सेलेक्टिव स्टडी करना बहुत ज़रूरी हैं l कक्षा 12वीं की Chemistry में कुछ कांसेप्ट CBSE और UP की बोर्ड परीक्षाओं के लिए बेहद महत्वपूर्ण है l इन Concepts से जुड़े सवाल हर साल बोर्ड परीक्षा में पूछें जाते हैं l

किसी भी Topic को समझ कर याद करना अच्छी बात है मगर कुछ Derivations और Diagrams इतने ज़्यादा महत्वपूर्ण होते हैं उन्हें समझने के साथ-साथ लिखकर याद करना (या दूसरे शब्दों में रटना) बहुत ज़रूरी होता है l लिखकर याद करने का सबसे बड़ा फायदा यह होता है कि एग्जाम में आपको रिकॉल करने में समय नहीं लगता और आप बहुत कम समय में उत्तर लिख सकते हैं l

अगर हम पुराने 5 से 10 साल के पेपर्स की एनालिसिस करेंगे तो पाएंगे कि कुछ ख़ास कंसेप्ट्स पर हर साल सवाल पूछे जा रहे हैं l इस आर्टिकल में हमने CBSE 12वीं Chemistry के पुराने 5 साल के महत्वपूर्ण सवाल छांट कर यहाँ लिखे हैं l यह सवाल घुमा फिरा कर हर साल पूछे जा रहे हैं l अगर आप UP board या दूसरे State Boards के पेपर्स देखेंगे तो आप पाएंगे कि उन पेपर्स में भी कुछ इसी तरह के सवाल बार-बार पूछे गए हैं l

यहाँ पर हमने 2017 की बोर्ड परीक्षा के भी महत्वपूर्ण सवाल शामिल किए हैं l क्यूंकि यह मुमकिन है कि जिन कांसेप्ट से जुड़े हुए सवाल वर्ष 2017 की परीक्षा में 5 नंबर के पूछें गए हैं वह सवाल 2018 की परीक्षा में 2 या 3 नंबर में भी पूछे जा सकते हैं l

आईए जानते है ऐसे ही कुछ महत्वपूर्ण सवाल:

Question:

(a) Write the reactions involved in the following :

(i) Etard reaction

(ii) Stephen reduction

(b) How will you convert the following in not more than two steps :

(i) Benzoic acid to Benzaldehyde

(ii) Acetophenone to Benzoic acid

(iii) Ethanoic acid to 2-Hydroxyethanoic acid

(2017)

क्या नहीं लग रहा पढ़ाई में मन? ज़रा इन मॉडर्न तरीकों को आज़माओ और फिर देखो कमाल

Question:

(a) Write the product(s) in the following reactions:

(b) Give simple chemical tests to distinguish between the following pairs of compounds :

(i) Butanal and Butan-2-one

(ii) Benzoic acid and Phenol

Question:

(a) A 10% solution (by mass) of sucrose in water has a freezing point of

269·15 K. Calculate the freezing point of 10% glucose in water if the freezing point of pure water is 273·15 K.

Given:

(Molar mass of sucrose = 342 g mol^‒1)

(Molar mass of glucose = 180 g mol^‒1)

(b) Define the following terms :

(i) Molality (m)

(ii) Abnormal molar mass

(2017)

Question:

(a) 30 g of urea (M = 60 g mol^‒1) is dissolved in 846 g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23·8 mm Hg.

(b) Write two differences between ideal solutions and non-ideal solutions.

Question:

(a) Account for the following:

(i) Transition metals show variable oxidation states.

(ii) Zn, Cd and Hg are soft metals.

(iii) E^o value for the Mn3+/Mn2+ couple is highly positive (+ 1·57 V) as compared to Cr^3+/Cr²⁺.

(b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

यह 7 ट्रिक्स अपनाने से कोई भी बन सकता हैं गणित में ज़ीरो से हीरो

Question:

(a) Following are the transition metal ions of 3d series :

Ti⁴⁺, V²⁺, Mn³⁺, Cr³⁺

(Atomic numbers: Ti = 22, V = 23, Mn = 25, Cr = 24)

Answer the following:

(i) Which ion is most stable in an aqueous solution and why?

(ii) Which ion is a strong oxidising agent and why?

(iii) Which ion is colourless and why?

(b) Complete the following equations :

(i) 2 MnO^‒₄ + 16 H⁺ + 5 S^2‒ →

(ii) KMnO4 + Heat →

(2017)

Question

(2016)

Question

(2016)

Question

(2016)

Question

(2016)

Question

(2016)

Question

(2016)

Question

(a) For a reaction A + B → P, the rate is given by

 Rate = k[A] [B]²

 (i) How is the rate of reaction affected if the concentration of B is doubled?

 (ii) What is the overall order of reaction if A is present in large excess?

 (b) A first order reaction takes 30 minutes for 50% completion. Calculate the time required for 90% completion of this reaction.

 (log 2 = 0.3010)

(2015)

Question:

(a) Account for the following:

 (i) Acidic character increases from HF to HI.

 (ii) There is large difference between the melting and boiling points of oxygen and sulphur.

 (iii) Nitrogen does not form pentahalide.

 (b) Draw the structures of the following:

 (i) Cl F₃

 (ii) XeF₄

(2015)

Question:

(i) Which allotrope of phosphorus is more reactive and why?

 (ii) How the supersonic jet aeroplanes are responsible for the depletion of ozone layers ?

 (iii) F₂ has lower bond dissociation enthalpy than Cl₂. Why?

 (iv) Which noble gas is used in filling balloons for meteorological observations?

 (v) Complete the equation:

 XeF₂ + PF₅ →

(2015)

Question:

(a) Write the structures of main products when aniline reacts with the following reagents:

 (i) Br₂ water

 (ii) HCl

 (iii) (CH₃CO)₂O / pyridine

 (b) Arrange the following in the increasing order of their boiling point:

 C₂H₅NH₂, C₂H₅OH, (CH₃)₃N

 (c) Give a simple chemical test to distinguish between the following pair of compounds:

 (CH₃)₂NH and (CH₃)₃N

(2015)

Question:

(a) Account for the following:

(i) CI-CH2COOH is a stronger acid than CH3COOH

(ii) Carboxylic acids do not give reactions of carbonyl group.

(b) Write the chemical equations to illustrate the following name reactions:

(i) Rosenmund reduction

(ii) Cannizzaro's reaction

(c) Out of CH₃CH₂-CO-CH₂-CH₃ and CH₃CH₂-CH₂-CO-CH₃, which gives iodoform test?

(2014)

Question:

(a) Write the products formed when CH3CHO reacts with the following reagents:

(i) HCN

(ii) H₂N-OH

(iii) CH₃CHO in the presence of dilute NaOH

(b) Give simple chemical tests to distinguish between the following pairs of compounds:

(i) Benzoic acid and Phenol

(ii) Propanal and Propanone

(2014)

Question:

(i) With reference to structural variability & chemical reactivity, write the differences between lanthanoids & actinoids.

(ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.

(iii) Complete the following equations:

MnO₄^‒ + 8H⁺ + 5e^‒→

(iv) Out of Mn³⁺ & Cr³⁺, which is more paramagnetic & why?

(2014)

Question:

(a) Complete the following equation:

(i) Cr₂O₇^‒ + 2OH^‒ →

(ii) MnO₄^‒ + 4H⁺ + 3e^‒ →

(b) Account for the following:

(i) Zn is not considered as a transition element.

(ii) Transition metals form a large number of complexes.

(iii) The E₀ value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr^3+/Cr²⁺ couple.

(2014)

Question:

(a) Define the following terms:

(i) Molarity

(ii) Molal elevation constant (K_b)

(b) A solution containing 15 g urea (molar mass = 60 g/mol) per litre of solution in water has the same osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g/mol) in water. Calculate the mass of glucose present in one litre of its solution.

Question:

(a) What type of deviation is shown by a mixture of ethanol and acetone? Give reason.

(b) A solution of glucose (molar mass = 180 g/mol) in water is labelled as 10% (by mass) what would be the molality and molarity of the solution? (Density of solution = 1.2 g/ml)

(2014)

Question:

(a) State Raoult's law for a solution containing volatile components. How does Raoult’s law become a special case of Henry’s law?

(b) 1.00 g of a non-electrolyte solute dissolved in 50 g of benzene lowered the freezing point of benzene by 0.40 K. Find the molar mass of the solute.  (K_f for benzene = 5.12 K kg/ mol)

(2013)

Question:

Define the following terms:

(i) Ideal solution

(ii) Azeotrope

(iii) Osmotic pressure

(b) A solution of glucose (C₆H₁₂₆) in water is labelled as 10% by weight. What would be the molality of the solution? 
(Molar mass of glucose = 180 g/mol)

Question:

(a) Give reasons for the following:

(i) Mn³⁺ is a good oxidising agent.

(ii) E^o_M²⁺_/M values are not regular for fist row transition metals (3d series).

(iii) Although ‘F’ is more electronegative than ‘O’, the highest Mn fluoride is MnF₄, whereas the highest oxide is Mn₂O₇.

(b) Complete the following equations:

Question:

(a) Why do transition elements show variable oxidation states?

(i) Name the element showing maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z = 30).

(ii) Name the element which shows only +3 oxidation state

(b) What is lanthanoid contraction? Name an important alloy which contains some of the lanthanoid metals.

Question:

(a) How will you convert the following:

(i) Propanone to Propan-2-ol

(ii) Ethanal to 2-hydroxy propanoic acid

(iii) Toluene to benzoic acid

(b) Give simple chemical test to distinguish between:

(i) Pentan-2 -one and Pentan-3 -one

(ii) Ethanal and Propanal

(2013)

Question:

(a)Write the products of the following reactions:

(b) Which acid of each pair shown here would you expect to be stronger?

ये थे कुछ महत्वपूर्ण प्रश्न जो घुमा फिरा कर हर साल CBSE, ICSE और UP के बोर्ड एग्जाम में ज़रूर पूछे जाते हैं l एग्जाम में अच्छे मार्क्स लाने के लिए इन सवालों को और सवालों से जुड़े कंसेप्ट्स को बिल्कुल इग्नोर न करें l इसी आर्टिकल की तरह हम आपको अन्य विषयों के महत्वपूर्ण सवालों के बारे में भी बताएंगे l

इन पाँच तरीकों से बना सकते गणित को एक सरल और रोचक विषय, परीक्षा में आएंगे पूरे नंबर