6.02 × 1020 molecules of urea are present in 100 ml of its solution. The concentration of urea solution is
(Avogadro constant, NA= 6.02 × 1023 mol-1)
-
Solution
Moles of urea present in 100 ml of sol.=\(\frac{6.02\times 10^{20}}{6.02\times 10^{23}}\)
∴M=\(\frac{6.02\times 10^{20}\times 1000}{6.02\times 10^{20}\times 100}=0.01M\)
[∵M = Moles of solute present in 1L of solution]
25ml of a solution of barium hydroxide on titration with a 0.1 molar solution of hydrochloric acid gave a litre value of 35ml.The molarity of barium hydroxide solution was
-
Solution
25 × N= 0.1 × 35 ; N = 0.14
Ba(OH)2 is diacid base
hence N = M × 2 or M = N⁄2
= 0.07 M
The percentage weight of Zn in white vitriol [ZnSO4.7H2O] is approximately equal to 16(Zn=65, S=32, O=16 and H = 1)
-
Solution
Molecular weight of ZnSO4 .7H2O
= 65 + 32 + (4 × 16) + 7(2 × 1 + 16) = 287.
∴percentage mass of zinc (Zn)\(=\frac{65}{287}\times 100=22.65\)%
One litre hard water contains 12.00 mg Mg2+. Milli-equivalents of washing soda required to remove its hardness is :
-
Solution
Mg+++Na2CO3→MgCO3+2Na+
1 g eq. 1g eq.
1 g eq. of Mg2+ = 12 gof Mg2+= 12000 mg
= 1000 milli eq. of Na2CO3
∴12mg Mg++= 1 milli eq.Na2CO3
A metallic chloride contain 47.22% metal. Calculate the equivalent weight of metal.
-
Solution
Suppose weight of metallic chloride =100 gm
Then weight of metal = 47.22 gm
Weight of chlorine = 100 – 47.22 = 52.78 gm
∴Equivalent weight of metal =\(\frac{47.22}{52.78}\times 35.5= 31.76\)
The least count of an instrument is 0.01 cm. Taking all precautions, the most possible error in the measurement can be :
-
Solution
In case of instrumental error, most possible error is equal to the least count of the instrument. So, most possible instrumental error can be 0.01 cm for the instrument which has a least count 0.01 cm.
A gas is found to have formula (CO)n. If its vapour density is 56, the value of n will be:
-
Solution
As we know that,
Molecular mass = 2 × Vapour density
⇒(12 + 16)n = 2 × 56 ⇒n=112⁄28=4
With in crease of temperature, which of these changes?
-
Solution
Among all the given options molarity is correct because the term molarity involve volume which increases on increasing temperature.
Which of the following is the best example of law of conservation of mass?
100 ml of solution of H2O2 on decomposition gives 1500 ml of O2 at N.T.P. The H2O2 has the volume strength
-
Solution
Given 100 mL of H2O2 gives 1500 mL of O2 at NTP.
⇒1 mL of H2O2 gives 15 mL of O2 at NTP.As we know that when 1 mL of H2O2 gives 10 mL of O2 at N.T.P., the solution is called 10 volume H2O2 i.e., the volume strength of H2O2 is 10 volume.So, when 1 mL of H2O2 gives 15 mL of O2 at N.T.P., the volume strength of H2O2 is 15 voume.