What is a balanced chemical equation? Why should chemical equations be balanced?
A balanced chemical equation is an equation in which the number of each element are equal on the reactant side as well as in product side.
for example: BaCl2 + K2SO4 → BaSO4 + 2KCl
reactant side product side
Chemical equation should be balanced because only a balanced equation tells us the relative quantities of different reactants and product involved in the reaction.
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?
Design an experiment to demonstrate hydrotropism.
Find the power of a concave lens of focal length 2 m.
Why does menstruation occur?
Why are some substances biodegradable and some non-biodegradable?
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
What do you mean by a precipitation reaction? Explain by giving examples.
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue