31,32
show work plz and help asap

     31 (a) 4           32 (a) 5

                        (b) 7                 (b) 3

                        (c) 5                 (c) 5

                        (d) 3                 (d) 2

Significant Figures (sf) Rules:

1) Trailing zeroes are considered significant ONLY If a decimal point is provided.

2) Zeroes between the decimal point and number are NOT significant unless they are between numbers.

3) All digits in scientific notation are counted (disregard the exponent).

31 (a) 508.0              trailing zero so use rule 1  -->  sf = 4

   (b) 820,400.0      trailing zero so use rule 1  -->  sf = 7

   (c) 1.0200 x 10⁵   scientific notation so use rule 3 --> sf = 5

    (d) 807,000         no trailing zeroes so use rule 1 --> sf = 3

32 (a) 0.049450     zero between decimal point & #, use rule 2 --> sf = 5

    (b) 0.000482     zero between decimal point & #, use rule 2 --> sf = 3

    (c) 3.1587 x 10 ⁻⁸  scientific notation so use rule 3 --> sf = 5

    (d) 0.0084          zero between decimal point & #, use rule 2 --> sf = 2

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.