Why are food preservatives added to food? how does it effect the reaction?

What is the relation between concentration of reactants and the rate of chemical reaction?

How many moles of co2 are produced during the complete combustion of 3.6 moles of c2h6

Which of the following is an example of how telecommunication devices people do their jobs? a.) a security guard checks the time using a digital watch. b.) a banker does some quick math using a solar calculator. c.) a nurse uses a digital thermometer to take a patient’s temperature. d.) a construction worker reports in to his office using a cell phone.