What does the prefix "di" in dioxide represent?

When light strikes a plane mirror, images form in locations where light does not actually reach. it only appears to the observer as though the light were coming from this position. what type of image is formed?

Consider the following reaction at equilibrium. 2co2 (g) 2co (g) + o2 (g) h° = -514 kj le châtelier's principle predicts that the equilibrium partial pressure of co (g) can be maximized by carrying out the reaction a. at high temperature and high pressure b. at high temperature and low pressure c. at low temperature and low pressure d. at low temperature and high pressure e. in the presence of solid carbon

Chemistry worksheet - i am not sure what they are asking for exactly?