1. according to the law of conservation of mass, the total mass of the reacting substances is
a. sometimes more and sometimes less than the total mass of the products
b. always equal to the total mass of the products.
c. always less than the total mass of the products
d. always more than the total mass of the products

c. orbital shape i hope this is correct

option c: 1605.1 kj

the balanced chemical reaction for combustion of methane is as follows:

here, enthalpy formation of is -74.7 kj/mol, 0 kj/mol, -393.5 kj/mol and -241.82 kj/mol respectively.

the heat released or can be calculated as follow:

putting the values,

thus, heat released by combustion of 1 mol of methane is 802.54 kj/mol. thus, for 2 mol, heat released will be:

therefore, heat released by the combustion of 2 mol of methane is 1605.1 kj.