NEET Chemistry Questions: Some Basic Concepts in Chemistry
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An aqueous solution of 6.3g oxalic acid dihydrate is made upto 250 mL. The volume of 0.1 N NaOH required to completely neutralize 10 mL of this solution is
$ Equivalents of H_2C_2O_4 . 2H_2O in 10ml = Equivalents of NaOH $
$ \therefore { 6.3 \times 1, 0000 \over 63 \times 250 \times 0.1 } = V
= 40mL $
The pair of the compounds in which both the metals are in the highest possible oxidation state is
The oxidation states of various metals are :
(a) Fe = + 3, Co + 3
(b) Cr = + 6 , Mn + 7
(c) Ti = + 6, Mn + 4
(d) Co = + 3, Mn + 6
In the analysis of 0.0500 g sample of feldspar, a mixture of the chiorides of sodium and potassium is obtained, which weighs 0.1180 g. Subsequent treatment of the mixed chlorides with silver nitrate gives 0.2451g of silver chloride. What is the percentange of a sodium oxide and potassium oxide in feldspar ?
Suppose amount of NaCl in the mixture = ‘x’ g
The amount of KCl in the mixture = (0.118 - x) g
$ NaCl + AgNO_3 \rightarrow AgCl + NaNO_3 $
58.5 143.5
$ \therefore x { 143.5 \times x \over 58.5 } g ..... (i) $
$ Similarly AgCl obtained from KCl = { 143.5 \times (0.118 - x) \over 74.5 } g... (ii)$
But (i) + (ii) = 0.2451 g (Given)
Amount of NaCl = 0.0338 g
Amount of KCl = 0.0842 g
Now, $ 2NaCl =Na_2O $
117 62
0.0338 $ {0.0338 \times 62 \over 117 } = 0.0179 g$
$ % of Na_2O = { 0.0179 \times 100 \over 0.5 } = 3.58 \% ....$
A compound contains 28% of nitrogen and 72% of a metal by weight. Three atoms of the metal combine with two atoms of nitrogen. Find the equivalent weight of the metal.
$ Equivalent weight = { Atomic Weight \over Valency } $
The density of a $ 3M Na_2S_2O_3 solution is 1.25 g per mL, What is the molalities of Na^+ and S_2 O{ 2-} _3 $ ions ?
$ m = { 1000 M \over 1000d - MM_s } $
M = Molarity of solution
d = density of solution
$ M_s $ = Molar mass of solute
$ = { 1000 \times 3 \over 1000 \times 1.25 - 3 \times 158 } = 3.865 $
Haemoglobin present in blood contain 3.72% by mass iron. Calculate the number of iron atoms in 2.0g of haemiglobin.
How many moles of magnesium phosphate, $ Mg_3(PO_4)_2$ will contain 0.25 mole of oxygen atoms (AEEE 2006)
In one molecule of magnesium phosphate, 8 oxygen atoms are present. Thus, 1 mole of magnesium phosphate will contain 8 moles of oxygen. Hence, 0.25 moles of oxygen atoms are present in 81×0. 25=3.
The unit $ JPa ^ {-1} $ is equivalent to
$ { J \over Pa} = { Work \over Pressure} = { Nm \over Nm ^ {-2} } = m^ 3 $
The density of Al metal is 2.7 gcm-3. An irregularly shaped piece of aluminium weighing 40.0g is added to a 100mL graduated cylinder containing 50.0mL of water. upto what height the water level will rise in the cylinder ?
$ d = { m \over v } $
$ V = { m \over d } = { 40 \over 2.7 } = 14.8cm ^ 3 $
Water level in cylinder = 50+ 14.8 = 64.8 mL
In which of the following pairs percent compostion of element is not same ?
No explanation available.
What weight of CuO will be required to provide 200Kg copper
No explanation available.
Choose the proper option after studying following statement (T = True, F = False) 1. The percent composition of vinyl chloride and its polymer PVC are same. 2. The perecent compostion of phosphorous trioxide $ (P_2O_3)is half than that of its dimer phosphorous hexoxide (P_4O_6) $ for each of the elements present in them.
No explanation available.
Impure sample of ZnS contains 42.34% Zn. What is the percentage of pure ZnS in the sample ?
The question is asking to find the percentage of pure ZnS (Zinc Sulfide) in the impure sample. Since the impure sample contains 42.34% Zn, the remaining percentage (100% - 42.34% = 57.66%) corresponds to the Sulfur (S) element. The formula of ZnS is Zn:S = 1:1, so the percentage of pure ZnS in the sample is 63%.
If the atomic mass of carbon were set at 50 amu, what would be the value of Avogadro’s number ? (
No explanation available.
For which of the following compounds molecular weigh cannot be determined from atomic weights ?
No explanation available.