Answer:
ΔH°rxn = - 433.1 KJ/mol
Explanation:
- CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g)
⇒ ΔH°rxn = 4ΔH°HCl(g) + ΔH°CCl4(g) - 4ΔH°Cl2(g) - ΔH°CH4(g)
∴ ΔH°Cl2(g) = 0 KJ/mol.....pure element in its reference state
∴ ΔH°CCl4(g) = - 138.7 KJ/mol
∴ ΔH°HCl(g) = - 92.3 KJ/mol
∴ ΔH°CH4(g) = - 74.8 KJ/mol
⇒ ΔH°rxn = 4(- 92.3 KJ/mol) + (- 138.7 KJ/mol) - 4(0 KJ/mol) - (- 74.8 KJ/mol)
⇒ ΔH°rxn = - 369.2 KJ/mol - 138.7 KJ/mol - 0 KJ/mol + 74.8 KJ/mol
⇒ ΔH°rxn = - 433.1 KJ/mol
Lower the melting point
Explanation:
Salts helps to melt road by lowering the melting point. It acts as an impurity and generally, impurities low the melting point of substances.
Salts are used as an antifreeze.
- Water freezes at 0°C and forms ice/snow which can impede human and vehicular movement.
- When salt is added, it causes the depression of the freezing point by lowering it further.
- The freezing point is pegged back at -6°C.
- This way it takes more low temperature to freeze the water.
- The salt acts as an impurity and causes the depression of melting point and widening of the melting range.
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ANSWER: B) drying paint
EXPLANATION: Car manufacturers use UV radiation to dry the paint o the vehicle. The high reflectivity of infrared radiation helps to keep the car interior cool. It also gives advantages over convection heating. It can provide both high intensity and low intensity heat and is a low cost heat source when compared in dollars per unit of energy consumed. The IR heating also doesn't penetrate deeply and apply heating only on the outer surface.
