When carbon is burned in air, it reacts with oxygen to form carbon dioxide. when 20.4 g of carbon were burned in the presence of 66.2 g of oxygen, 11.8 g of oxygen remained unreacted. what mass of carbon dioxide was produced?

74.77 g

The equation for the reaction between carbon and Oxygen is given by;

C(s) + O₂(g) → CO₂(g)

We are given;

Mass of carbon 20.4 g

Mass of Oxygen is 66.2 g

Remaining mass of Oxygen after the reaction is 11.8 g

Therefore, Carbon is the rate limiting reagent since Oxygen was in excess.

We are required to calculate the mass of carbon dioxide produced.

Moles = Mass ÷ Molar mass

Molar mass of carbon = 12.01 g/mol

Therefore;

Moles of Carbon = 20.4 g ÷ 12.01 g/mol

                           = 1.699 moles

From the equation, 1 mole of carbon reacts to produce 1 mole of carbon dioxide.

Therefore, the mole ratio of Carbon to carbon dioxide is 1 :1

Thus, moles of carbon dioxide = Moles of carbon

                                                  = 1.699 moles

Mass = Moles × Molar mass

Molar mass of carbon dioxide = 44.01 g/mol

Therefore;

Mass = 1.699 moles × 44.01 g/mol

         = 74.77 g

Therefore, the mass of carbon dioxide gas produced is 74.77 g

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: