What is the number of significant figures in Avogadro's number `(6.0 xx 10^(23))` and Planck's constant `(6.62 xx 10^(-34) J s)`.

Answer

(i) 2 (ii) 2

Explanation

(i) Zeros to the right of the decimal point are significant.
(ii) Zeros to the left of the first non-zero digit are not significant.
(iii) When expressed as `7.5xx10^(4)`, only significant figures of 7.5 are to be considered.
(iv) Apply rules given in Hints (i) and (ii) above.
(v) `67.32-6.3=61.01`. The result is to be reported to same number of decimal places as that of the term with least number of decimal places (viz 6.3 with only one decimal place). Hence, after rounding off, reported result = 61.0, (which has there significant figures).
(vi) `4.2+7.589=11.789`. As it is to be reported to one decimal place (as in (v) above), after rounding off, reported result = 11.8 (having three significant figures).
(vii) As least precise term ( viz 3.6 ) has two significant figures, the reported result should have two significant figures.
(viii) Leaving exact number 2, the least precise term (8.1) has two significant figures.