NEET Chemistry Questions: Some Basic Concepts in Chemistry

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Which one of the following contains greatest number of oxygen atoms ?





No explanation available.
How many g of NaOH can be obtained by reaction of 1 Kg of $ Na_2CO_3 with Ca(OH)_2 $ ?




The reaction between Na₂CO₃ and Ca(OH)₂ produces 2NaOH and CaCO₃. Given 1kg (1000g) of Na₂CO₃, the mass of NaOH produced can be calculated as: (2 × 40g/mol) / (106g/mol) × 1000g = 755g. Therefore, 755g of NaOH can be obtained from the reaction of 1kg of Na₂CO₃ with Ca(OH)₂.

Oxidation number of sodium in sodium amalgam is





In sodium amalgam, which is an alloy of sodium and mercury, the oxidation state of sodium is zero. This is because sodium loses its valence electron to mercury, forming a stable ionic compound where sodium has an oxidation state of +1 and mercury has an oxidation state of -1.
Calculate the amount of NaOH required to neutralize 100 mL 0.1M $ H_2SO_4$ .




$ 0.1MH_2SO_4 = 1000mL solution contains 0.1 mol H_2SO_4 $ $ \therefore 100mL solution contains 0.01 mol H_2SO_4 $ $ \therefore mass of H_2SO_4 = 0.01 \times 98 = 0.98g $ $ 2NaOH + H_2SO_4 \rightarrow Na_2SO_4 + 2H_2O $ 2(40)g 98g (?) 0.98g $ = { 80 \times 0.98 \over 98 } = 0.8g $
3g of an oxide of a metal is converted into chloride and it yielded 5 g of chloride. Find the equivalent weight of the metal.




$ { Wt. of metal oxide \over Wt. of metal Choride } = { Eq. wt. of metal + Eq. wt. of oxide \over Eq. wt. of metal + Eq. wt. of Choride } $ $ \therefore { 3 \over 5 } = { E + 8 \over E + 35.5 } \therefore E = 33.25 $
A compound contains two oxygen atoms, four carbon atoms and number of hy drogen atoms is double of carbon atoms. What is the density of vapour of this compound ?




$ M .F. C_4 H_8O_2 $ $ \therefore Molar mass = 88 $ $ Vapour density = 88 / 2 = 44 $

The number of molecules in 100 mL of each of $ O_2,NH_3 $ and $ CO_2 $ at STP are





Equal volumes under identical conditions contain equal no. of molecules

Which of the following represents the formula of a compound which contains 26% nitrogen and 74% oxygen ?




$ N_{26 \over 14 } O_{74 \over 16 } = N_{1.85} O_{4.625 } \Rightarrows N_2 O_5 $
$ NKg^{-1} $ is the unit of




$ F = ma $ $ a = { f \over m} = { N \over Kg } = N Kg ^ {-1} $
Which one of the following statements is incorrect ?




No explanation available.
A balanced chemical equation is in accordance with




A balanced chemical equation satisfies the law of conservation of mass, which states that mass can neither be created nor destroyed in a chemical reaction. The total mass of the reactants must equal the total mass of the products in a balanced chemical equation.
The atomic weights of two elements X and Y are 20 and 40 respectively. If ‘a’ gm of X contains ‘b’ atoms, how many atoms are present in ‘2a’ gm of Y ?




$ No of moles of X = { a \over 20} $ $ \therefore No.of atoms of X = {a \over 20 } \times N =b (given ) $ $ \therefore a = { 20b \over N} $ $ No.of moles of Y = { 2a \over 40 } $ $ \therefore No.of atoms of Y = { 2a \over 40 } \times N $ $ = { 2 \over 40 } \times {2o b \over N } \times N = b $
If the components of air are $ N_2 ,78 \%, O_2, 21 \% ; Ar, 0.9 \% and CO_2, 0.1 \% $ by volume, what will be the molecular weight of air ?




$ Mol. wt. of air = { 78 \times 28 + 21 \times 32 + 0.9 \times 40 + 0.1 \times 44 \over 78 + 21 + 0.9 + 0.1 } $
Calculate the molarity of a solution obtained by mixing $ 50mL of 0.5M H_2SO_4 and 75 mL of 0.25M H_2SO_4 $ .




$ No.of moles of 0.05L H_2SO_4 = 0.5 \times 0.05 = 0.025 $ $ No.of moles of 0.075L H_2SO_4 = 0.25 \times 0.075 = 0.01875 $ $ \therefore Total no. of moles = 0.025 + 0.01875 = 0.04375 $ Total vol = 0.05L + 0.075L = 0.125L $ \therefore Molarity = { 0.04375 \over 0.125 } = 0.35 M $
Which of the following has the highest normality ?




Normality is a measure of the concentration of a solution and is defined as the number of gram-equivalent weights of the solute present per liter of the solution. Among the given options, 1 M H3PO4 has the highest normality of 3 as it can provide 3 H+ ions per molecule upon dissociation.