Both chemical and physical changes can involve a change in appearance. This is because, during a chemical change, the substance may change color. A physical change that changes color would be, for example, adding food coloring to water.
For ever 1 mole of nitrogen you need 3 moles of hydrogen to make 2 moles of Ammonia.
We only have 10 moles of hydrogen so that is the limiting as there is more nitrogen then hydrogen in this particular case.
Therfore the ratio is 2 ammonia to 3 hydrogen [2:3]
Do 2/3which is 0.6667. This is how many moles of ammonia you get per mole of hydrogen.
Multiply that by 10 and you get 6.67 moles of Ammonia produced [3 significant figures]
The answer to this question is 1s^2.