The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound
(a) is always negative
(b) is always positive
(c) may be positive or negative
(d) is never negative

Q. The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound

Q. State true or false.
(i) The product of a negative and a positive integer may be zero.
(ii) The product of two negative integers is always positive.
(iii) The product of two integers with opposite signs is the same as the product of their absolute values.
(iv) If exactly one of the three given integers is negative, then product is always negative.
(v) The product of any two positive or any two negative integers is always smaller than the integers.

Q. The standard enthalpies of elements in their standard(natural) states are taken as zero. On basis of this statement, we can say that the enthalpy of formation of a compound :

Q.

Question 15

When a negative integer is subtracted from another negative integer, the sign of the result

(a) is always negative

(b) is always positive

(c) is never negative

(d) depends on the numerical value of the integers

Q. Which of the following statements are true?
(i) The product of a positive and a negative integer is negative.
(ii) The product of three negative integers is a negative integer.
(iii) Of the two integers, if one is negative, then their product must be positive.
(iv) For all non-zero integers a and b, a × b is always greater than either a or b.
(v) The product of a negative and a positive integer may be zero.
(vi) There does not exist an integer b such that for a> 1, a × b = b × a = b.