Which of the following is an example of pure research? searching for fuels other than gasoline to power cars producing heat-resistant plastics for use in household ovens creating synthetic elements to study their properties finding ways to slow down the rusting of iron ships

I think the correct answer would be the third option. An example of a pure research would be creating synthetic elements to study their properties. Pure research is also known as fundamental or basic research. It has an exploratory nature wherein it is done without any end use in mind. It is mostly out of the curiosity or intuition of a researcher. Most of the study under this type is aiming to advance an existing knowledge by explaining or identifying the relationship of the variables being studied. It is aimed at improving theories in order to the understanding of a specific  phenomenon. 

Yes you are correct use the scientific method

The formula is (nh4)2co3