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 %

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.