AISSCE DATE SHEET 2012

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Fast Review – Chemical Bonding and Molecular Structure

IN THE EXAMINATION HALL
• Try to think positive and maintain positive attitude giving the test.
• Once in the hall, take time to settle down and set your table.
• Ignore symptoms of anxiety and focus on your task.
• Do not hurry into reading the question paper.
• Read the directions slowly and carefully. If there are any doubts clarify with the instructor, teacher or invigilator.
• Feel comfortable before you start your answers. ... Read more »

A simple voltaic cell has two major defects. They are

1. Local action and
2. Polarisation

1. Local Action : This is caused by the impurities present in zinc rod. When the zinc rod isimmersed in acid, the zinc atoms and the impurity atoms form a large number of local cells and the zinc rod gets consumed even when the cell is not in use. This defect can be avoided by using amalgamated zinc rods. Mercury dissolves zinc and allows only zinc atoms to come into contact with acid and thus avoids formation of local cells.
2. Polarisation: The hydrogen ions reaching the negative electrode get accumulated preventing further neutralization of hydrogen ions. This results ... Read more »

C contains many operators, and because of the way in which operator precedence works, the interactions between multiple operators can become confusing.

x=5+3*6;

X receives the value 23, not 48, because in C multiplication and division have higher precedence than addition and subtraction.

char *a[10];

Is a a single pointer to an array of 10 characters, or is it an array of 10 pointers to character? Unless you know the precedence conventions in C, there is no way to find out. Similarly, in E.11 we saw that because of precedence statements such as *p.i = 10; d ... Read more »