The rate law is given by:
\[
\text{rate} = k[\mathrm{H}_{2}]^{2}[\mathrm{NH}_{3}]
\]
The exponent of \([\mathrm{H}_{2}]\) in the rate law is 2. Therefore, the reaction order with respect to \(\mathrm{H}_{2}\) is 2.
The exponent of \([\mathrm{NH}_{3}]\) in the rate law is 1. Therefore, the reaction order with respect to \(\mathrm{NH}_{3}\) is 1.
The overall reaction order is the sum of the exponents in the rate law. Therefore, the overall reaction order is:
\[
2 + 1 = 3
\]
The initial rate of reaction is given as \(91.0 \, \mathrm{M/s}\). If the concentration of \([\mathrm{H}_{2}]\) is doubled, the new rate can be calculated using the rate law:
\[
\text{New rate} = k(2[\mathrm{H}_{2}])^{2}[\mathrm{NH}_{3}]
\]
This simplifies to:
\[
\text{New rate} = 4k[\mathrm{H}_{2}]^{2}[\mathrm{NH}_{3}] = 4 \times 91.0 \, \mathrm{M/s} = 364 \, \mathrm{M/s}
\]
- Reaction order in \(\mathrm{H}_{2}\): \(\boxed{2}\)
- Reaction order in \(\mathrm{NH}_{3}\): \(\boxed{1}\)
- Overall reaction order: \(\boxed{3}\)
- New initial rate when \([\mathrm{H}_{2}]\) is doubled: \(\boxed{364 \, \mathrm{M/s}}\)