The boiling points of HF, H2O and NH3 increase in the order of
NH3
H2O < HF
HF < NH3 < H2O
NH3 < HF < H2O
Correct answer is D
Ammonia = -33.34°C; Hydrogen fluoride = 19.5°C; Water = 100°C
A difference between chemical and physical change is that in a chemical change
oxygen is consumed
heat is supplied
the reversible process occurs
a new substance is formed
Correct answer is D
In chemical change a new substance is formed while in physical change no new substance is formed. Options A,B,C are all properties of a physical change
Detergents are manufactured with straight hydrocarbon chains, is to make them
soluble
biodegradable
cheaper
foamy
Correct answer is B
Biodegradable because the straight hydrocarbons are natural and slightly soluble in water. Options A,C,D do not have strength hydrocarbon chains and they could harm the environment if they are made with the detergent
When sugar is dissolve in tea, the reaction is accomplished by?
positive change
negative entropy change
no entropy change
a minimum entropy change
Correct answer is C
There is no disorderliness so no entropy change.
The elements that belong to the third period of periodic table are
Li, Be, Al and D
Na, P, O and Cl
B, C, N, and O
Na, Mg, S and Ar
Correct answer is D
Na, Mg, S and Ar is the set of elements that belong to third period of the periodic table. Option A,B,C have elements which belong to the other period in the periodic table included in them.