Some Basic Concepts of Chemistry - Online Test

Answer : Option B
Explaination / Solution:

Stoichiometry is a method to express quantitative aspects of a chemical reaction . Usually , the masses of reactants as well as those of products in a chemical reaction are calculated using corresponding balanced chemical equation . It is convenient and hence desirable to calculate volumes of gaseous reactants and products .

Answer : Option D
Explaination / Solution:

Molecular mass of Glucose is calculated  using the relation :

Molecular mass

 =    ∑ ( 6*atomic mass of  C , 12* atomic mass of H  ,  6* atomic mass of  O )  u    

∴     substituting the respective atomic masses  we get ,

   Molecular mass of  glucose ( C6  H12 O6 )

 = [  6(12.0107)+12(1.008)+6(15.9994) ]

= 180.162 u.

Answer : Option D
Explaination / Solution:

Stock solution can best be described as concentrated solution of known accurate concentration that will be used for future laboratory use. Since large amounts of solutes are used for preparing stock solution a more accurate concentration of it can be achieved quite easily, and as such the chances are slim to get erroneous results of the related experiments.. In addition , stock solutions are generally more stable as compared to working solution since they usually do not suppport bacterial growth. A multiple working solution can be prepaed by dilution of stock solution using easy calculation and process.

Answer : Option D
Explaination / Solution:

Molality is defined as no. of moles of solute present per kg of solvent.It is denoted as " m " . Mathematically , Molality (m) = [ number of moles of the solute ] / kg of solvent Since , this mode of expressing the strength of a solution involves ( weight / weight ) relationship of solute and solvent , the molality of the solution is not affected by variation in temperatures of the solution.

Answer : Option C
Explaination / Solution:

The given equation  gets balanced by inserting the coefficients   (3 , 1  ,1  ,3 )  in blank spaces from LHS to RHS .  Thus, the balanced equation for the given reacion is ,

 3KOH + H3PO4 → K3PO4 + 3H2O.

Answer : Option B
Explaination / Solution:

The balanced equation for the given equation is ,

hence , the coefficients ( 8 ,17 , 1, 8 ) are inserted on blank spaces ( from LHS to RHS )

Answer : Option A
Explaination / Solution:

The given equation gets balanced by inserting coefficients  ( 4 , 3 , 2  )  in  blank spaces  from LHS to  RHS ) . The balanced equation is - 

Answer : Option D
Explaination / Solution:

The given equation gets stoichiometrically balanced when the coefficients ( 1 , 6 , 3 ,  2 )  starting from LHS to RHS are inserted in  given blank spaces .

Thus , the balanced equation for the reaction is ,

 

Answer : Option A
Explaination / Solution:

The gram molar mass of Ca CO3  is calculated by ,

(i) adding up the atomic masses of  Ca  ,  C   &  3 O  atoms   &  ,

(ii) representing the molar mass in grams.

Thus , gram molar mass of Ca C O3  

=   Σ [ atomic mass of  Ca   , atomic mass of C    , 3  x  atomic mass of O    ]

 =  [40+12+(3X16)]g$$

=  ( 40  +  12  +  48 ) g 

=100g 

 It  should be noted that  ,

atomic mass of  Ca 

=  12 

atomic mass of  C

=  12

atomic mass of  O

=  16

Answer : Option C
Explaination / Solution:

Molar mass of CO2  =  Σ (atomic mass of  C  , 2*atomic mass of  O )  

=   [12+2(16)] u

Since , gram molar mass 

=  Molar mass expressed in gms .  

∴$\therefore$  gram molar mass of CO2 

=  44 g