Heat of combustion.<span> The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat.</span>
Answer:
a.52.9 km/h
b.90 km
Explanation:
We are given that






Time spend on eating lunch and buying ga=15 min.
a.Total time=30+12+45+15=102 minute=
1 hour=60 minutes
Distance=



Total distance=
Average speed=
Using the formula
Average speed=
b.Total distance between the initial and final city lies along the route=90 km
It magnifies light received from distant objects.
Double displacement: parts of compounds switch places to form two new compounds
FYI
decomposition: a complex substance breaks down into two or more simple substances
Single displacement: a single substance replaces another substance in a compound
<span>Synthesis: two simple substances combine to form a new complex substance</span>