Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
HCl or HNO3 shows acidic character on aqueous solution because hydrogen ions dissociation always occurs in the presence of water. Hydrogen ions (H+) when combined with H2O to form hydronium ions (H3O+).
The reaction is as follows:
HCL(aq) → H+ + CL-
H+ + H2O → H3O+
Whereas aqueous solutions of glucose and alcohol contain hydrogen, these cannot dissociate in water to form hydrogen ions. Therefore they do not show acidic character.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
(a) mass (b) speed
(c) velocity (d) momentum
Give an example of a double displacement reaction other than the one given in activity 1.10.
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Why are some substances biodegradable and some non-biodegradable?
What are the limitations of extracting energy from—
(a) the wind? (b) waves? (c) tides?
What does one mean by exothermic and endothermic reactions? Give examples.
Suggest some approaches towards the conservation of forests.
What is the principle of an electric motor?