Calcuate the percent by mass . best answer would be the brainliest
1) nitrogen in mg (cn)2
2) potassium in khco3
3) hydrogen in nh3

1) 36.70 %; 2) 39.05 %; 3)17.75 %

Step-by-step explanation:

% of element = Mass of element/mass of compound × 100 %

1) N in Mg(CN)₂

The masses of each element are:

1Mg  = 1  × 24.30 = 24.30 u

2C    = 2 × 12.01  = 24.02 u

2N    = 2 × 14.01  = 28.02 u

              TOTAL = 76.34  u

% N = 28.02/76.34 × 100 %

      = 36.70 %

2) K in KHCO₃

The masses of each element are:

1K  = 1 × 39.10    =   39.10   u

1H = 1 ×     1.008 =     1.008 u

1C = 1 ×  12.01     =     2.01   u

3O = 3 ×  16.00   = 48.00   u

           TOTAL    = 100.12    u

% N = 39.10/100.12 × 100 %

      = 39.05 %

3) H in NH₃

The masses of each element are:

1N  = 1 × 14.01   = 14.01   u

3H = 3 ×    1.008 =   3.024 u

                TOTAL   = 17.03   u

% N = 3.024/17.03 × 100 %

        = 17.75 %

2b2t

explanation:

2b2t

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".