Some Basic Concepts of Chemistry
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<p><strong>1.43. The mass of one atom of C-12 in grams is:</strong></p>
<p><strong>(a)</strong> 6.022 × 10<sup>23</sup> g</p>
<p><strong>(b)</strong> 6.022 × 10<sup>23</sup> kg</p>
<p><strong>(c)</strong> 1.99 × 10<sup>–23</sup> g</p>
<p><strong>(d)</strong> 1.99 × 10<sup>–23</sup> kg</p>
1.41. Assertion: In chemical reactions, the reactant, which gets consumed first, limits the amount of product formed and is called the limiting reagent.
R: Stoichiometry deals with the calculation of masses (sometimes volumes also) of the reactants and the products involved in a chemical reaction.
1.41. Assertion: In chemical reactions, the reactant, which gets consumed first, limits the amount of product formed and is called the limiting reagent.
R: Stoichiometry deals with the calculation of masses (sometimes volumes also) of the reactants and the products involved in a chemical reaction.
1.41. (b) Both the statements are correct but the second statement is not the actual reason for the first statement.
Many a times, reactions are carried out with the amounts of reactants that are different than the amounts as required by a balanced chemical reaction. In such situations, one rea
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1.40. Assertion: SI unit of volume is L (litre).
R: But again, in chemistry laboratories, volumes is often denoted in cm3 or dm3 units.
1.40. Assertion: SI unit of volume is L (litre).
R: But again, in chemistry laboratories, volumes is often denoted in cm3 or dm3 units.
1.40. (d) Volume is the amount of space occupied by a substance. It has the units of (length)3. In SI system, volume has units of m3. Smaller volumes are denoted in cm3 or dm3 units. A common unit, litre (L) which is not an SI unit, is used for measurement of volume of liquids.
Upvote 1.39. Assertion: Volume of a gas is inversely proportional to the number of moles of gas.
Reason: The ratio by volume of gaseous reactants and products agrees with their mole ratio.
1.39. Assertion: Volume of a gas is inversely proportional to the number of moles of gas.
Reason: The ratio by volume of gaseous reactants and products agrees with their mole ratio.
1.39. (d) Taking reference of the ideal gas equation PV= nRT (Where, P= Pressure, V= volume, n=no of moles, R= gas const, T= temperature). It can thus be concluded that volume is directly proportional to the no. of moles.
Upvote 1.38. Assertion: 123.00 has three significant figures.
Reason: All numbers right to the decimal point are significant.
1.38. Assertion: 123.00 has three significant figures.
Reason: All numbers right to the decimal point are significant.
1.38 (d) 123.00 has five significant figures. Assertion is wrong statement while reason is a correct statement.
Upvote Assertion Type Questions:
1.37. Assertion: One mole of any gas contains 6.022 x 1023 molecules.
Reason: 1 g of any gas contains equal number of moles.
Assertion Type Questions:
1.37. Assertion: One mole of any gas contains 6.022 x 1023 molecules.
Reason: 1 g of any gas contains equal number of moles.
1.37. (c) Equal moles of different substances contain same number of constituent particles but equal weights of different substances do not contain the same number of constituent particles due to the difference in their molar mass.
Upvote 1.36. Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction.
4 HCl (aq) + MnO2 (s) ———–> 2 H2O (l) + MnCl2(aq) +Cl2(g)
How many grams of HCl react with 5.0 g of manganese dioxide? (Atomic mass of Mn = 55 u
1.36. Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction.
4 HCl (aq) + MnO2 (s) ———–> 2 H2O (l) + MnCl2(aq) +Cl2(g)
How many grams of HCl react with 5.0 g of manganese dioxide? (Atomic mass of Mn = 55 u
1.36. The molar mass of MnO2is 87g and the molar mass of HCl is 36.5 g.
According to the equation, 4 moles of HCl (i.e. 4 x 36.5g = 146 g) reacts with 1 mol of MnO2 (87g).
So, for 5.0 g of MnO2 will react with:
= 5 x146/87 = 8.40 g of MnO2
Therefore, 8.4 g of HCl will react with 5 g of MnO2.
Upvote 1.35. Calcium carbonate reacts with aqueous HCl according to the reaction
CaCO3 (s) + 2HCl (aq) ———->CaCl2 (aq) +CO2(g) +H2O(l).
What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?
1.35. Calcium carbonate reacts with aqueous HCl according to the reaction
CaCO3 (s) + 2HCl (aq) ———->CaCl2 (aq) +CO2(g) +H2O(l).
What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?
1.35. Step 1: 0.75 M HCl means 0.75 mol per 1000 mL or 0.75 x 36.5 g in 1000 mL.
i.e. 1000 mL of 0.75 M HCl contains 0.75 x 36.5 g HCl
Therefore, 25 mL of 0.75 M HCl contains 0.75 x 36.5 x 25/ 1000 g = 0.6844 g
Step 2: To calculate mass of CaCO3reacting completely with 0.6844 g of HCl
Ca
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