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Practice each question, then open the answer or worked solution.
Which of the following represents a correct chemical formula? Name it.
Answer is (b) BiPO4, Its name is Bismuth Phosphate
Explanation:
Bismuth phosphate is right because Both ions are trivalent Bismuth phosphate(Bi3+- Trivalent anion. anion is an ion that is negatively charged).
Write the molecular formulae for the following compounds
(a) Copper (II) bromide
(b) Aluminium (III) nitrate
(c) Calcium (II) phosphate
(d) Iron (III) sulphide
(e) Mercury (II) chloride
(f) Magnesium (II) acetate
Answers are
(a) Copper (II) bromide = CuBr2
(b) Aluminium (III) nitrate = Al(NO3)3
(c) Calcium (II) phosphate = Ca3(PO4)2
(d) Iron (III) sulphide = Fe2S3
(e) Mercury (II) chloride = HgCl2
(f) Magnesium (II) acetate = Mg(CH3COO)2
Write the molecular formulae of all the compounds that can be formed by the combination of following ions Cu2+, Na+, Fe3+, Cl– SO4 -2, PO4 -3
Answers are
CuCl2/ CuSO4/ Cu3(PO4) 2
NaCl/ Na2SO4/ Na3PO4
FeCl3/ Fe2(SO4) 3 / FePO4
Write the cations and anions present (if any) in the following compounds
(a) CH3COONa
b) NaCl
(c) H2
(d) NH4NO3
Give the formulae of the compounds formed from the following sets of elements
(a) Calcium and fluorine
(b) Hydrogen and sulphur
(c) Nitrogen and hydrogen
(d) Carbon and chlorine
(e) Sodium and oxygen
(f) Carbon and oxygen
(a) Calcium and fluoride – Calcium Fluoride (CaF2)
(b) Hydrogen and sulphur- H2S- Hydrogen Sulphide
(c) Nitrogen and hydrogen- NH3- Ammonia
(d) Carbon and chlorine – CCl4- Carbon Tetrachloride
(e) Sodium and oxygen – Na2O-Sodium Oxide
(f) Carbon and oxygen- CO2 ; CO- Carbon-di-oxide; Carbon Monoxide
Which of the following symbols of elements are incorrect? Give their correct symbols
(e) Sodium So
Cobalt CO is wrong, correct symbol is Co
Carbon c is wrong, correct symbol is C
Aluminium AL is wrong, correct symbol is Al
Helium He is the right symbol
Sodium So is wrong, correct symbol is Na
Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them. (You may use appendix-III).
(a) Ammonia
(b) Carbon monoxide
(c) Hydrogen chloride
(d) Aluminium fluoride
(e) Magnesium sulphide
|
S. No. |
Compounds | Chemical formula | Ratio by mass of the combining elements |
| (a) | Ammonia | NH3 |
N:H=14:3 |
|
(b) |
Carbon monoxide | CO | C:O= 12:16=3:4 |
| (c) | Aluminium fluoride | HCl |
H:Cl= 1:35.5 |
|
(d) |
Aluminium fluoride | AlF3 | Al:F=27:57=9:19 |
| (e) | Magnesium sulphide | MgS |
Mg:S= 24:32=3:4 |
State the number of atoms present in each of the following chemical species
(a) CO3-2
(b) PO4-3
(c) P2 O5
(d) CO
(a) CO3-2 – 1+3=4
(b) PO4-3 – 1+4=5
(c) P2O5 – 2+5=7
(d) CO – 1+1=2
What is the fraction of the mass of water due to neutrons?
Mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams.
Mass of one mole (Avogadro Number) of neutrons =1g
Mass of one neutron = 1/ Avogadro number(NA) g
Mass of one molecule of water = Molar mass / NA = 18/ NA g
The molar mass of water is 18.015 g/mol. This was calculated by multiplying the atomic weight of hydrogen (1.008) by two and adding the result to the weight for one oxygen (15.999)
Mass of one molecule of water = Molar mass / NA = 18/ NA g
Avogadro number(NA) =6.022 x 1023mol¯1
There are 8 neutrons in one atom of oxygen
Number of neutrons in oxygen= number of oxygen – Atomic number of oxygen
Oxygen’s atomic weight= 15.9994
increases with an increase in temperature.
Therefore the mass is 16
Therefore number of neutrons= 16 – 8 = 8
Mass of one neutron = 1/ Avogadro number(NA) g
Mass of 8 neutrons = 8/ Avogadro number(NA) g
Fraction of mass of water due to neutrons = 8/18 g
Does the solubility of a substance change with temperature? Explain with the help of an example.
Solubility is the ability of a solute to get dissolved in 100g solvent. Solubility of a given solute to dissolve in specific solvent depends on the temperature. With an increase in temperature solubility of liquids and solids increase. In the same way solubility of gases decreases with increase in temperature.
Ex: Sugar dissolves faster in hot water than in cold water.