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Chemical formula

Example: Balanced Chemical Equations with Subscripts Water: $$\ce{H2O}$$ Carbon dioxide: $$\ce{CO2}$$ Iron(III) hydroxide (Rust reaction): $$\ce{4Fe + 3O2 + 6H2O -> 4Fe(OH)3}$$ Copper(II) sulfate pentahydrate: $$\ce{CuSO4 * 5H2O}$$ Chemical Formulas in Chemistry Chemical formulas are the symbolic representations of chemical substances. They show the elements present in a compound and the ratio in which the atoms of these elements combine. Chemical formulas are essential for understanding the composition, structure, and behavior of compounds in chemical reactions. 1. What is a Chemical Formula? A chemical formula uses symbols of elements and numerical subscripts to represent the composition of a substance. For example, the formula for water is: $$ \ce{H2O} $$ This indicates that each water molecule is made up of 2 atoms of hydrogen and 1 atom of oxygen. 2. Types of Chemical Formulas Empirical Formula Molecular Formula Structural Formula...
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IIT Practice Paper

1. If x^2 + y^2 = 1 , then 
 
  (a) yy" - (2y')^2 + 1 = 0 
  (b) yy" + (y')^2 + 1 = 0 
  (c) yy" -  (y')^2  - 1 =0 
  (d) yy" + 2(y')^2 + 1 =0 

Answer : (b) 

2. If f(x) has domain [ -2 , 5 , 2 ] , the domain of f([|x|]) is 

 (a) -3 < = x < =2 
 (b) -3 < x < = 2 
 (c) -2 < = x < = 2 
 (d) all of them 

Answer : (c) 

3. Area bounded by the curve y = x^3 , the x axis and the ordinates x = -2 and x = 1 , is 

 (a) -9 
 (b) -15/14
 (c) 15/14 
 (d) 17/4 

Answer : (d)

4. Oxidation number and coordination number of silver in Tollen's reagent respectively are 

 (a) 1,1 
 (b) 2,1
 (c) 2,2
 (d) 1,2 

Answer : (d) 

5. Which of the following is not a transition element ? 
 (a) Zn 
 (b) Ru
 (c) Ag
 (d) Pb

Answer : (d) 

6. Which of the following on heating does not give nitrogen gas ? 
 
  (a) NH4NO3
  (b) NH4NO2
  (c) Ba(N3)2
  (d) (NH4)2Cr2O7 

Answer : (a) 

7. The ore having two different metal atoms is 
 
 (a) haematite
 (b) galena 
 (c) magnetite 
 (d) copper pyrites 

Answer : (d) 

8. Adsorption is accompanied by 

 (a) decrease in enthalpy and increase in entropy 
 (b) increase in enthalpy and increase in entropy 
 (c) decrease in enthalpy and decrease in entropy 
 (d) no change in enthapy and entropy 

Answer : (c) 

9. A vertical cylinder closed at both ends is fitted with a smooth piston dividing the volume into two parts each containing one mole of air . At the equilibrium temperature of 320 K.  the upper and lower parts are in the ratio 4:1 . The ratio will become 3:1 at a temperature of : 

(a) 450 K 
(b) 228 K 
(c) 420 K 
(d) 570 K 

Answer : (a) 

10. The ratio of densities of nitrogen and oxygen is 14:16 . At what temperature the speed of sound in oxygen will be the same which in nitrogen at 15°C ? 

 (a) 56.1°C 
 (b) 40°C 
 (c) 38°C
 (d) 64°C 
 
Answer : (a) 




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