What is the value of n in ch3 (ch2) nch3 if the name of the hydrocarbon is heptane?

The value that n must be in the organic compound is that it must be 5. This will result in the name of the hydrocarbon to be heptane as heptane possess 7 carbons in the longest parent chain. So the formula would be CH3 (CH2) 5CH3. Distributing the 5 inside and making it a subscript to the carbon gives us 5. Adding up all of the carbons together should give you the correct number of carbon atoms with respect to its name, heptane. 1+5+1 = 7.