Answer:
D. A compound can be separated into two or more elements through a chemical reaction.
Explanation:
By method of elimination, we are going t obtain the correct option.
A. A compound is made up of a single atom.
This is wrong because, a compound can contain more than one atom. An example is H2O
B. A compound is made up of many atoms that are all the same type.
This is wrong because a compound can contain atoms of different elements. An example is H2O. It contains atoms of hydrogen and oxygen.
C. A compound can be separated into two or more elements through physical processes.
This is wrong. H2O being a compound cannot be separated by ordinary physical means.
D. A compound can be separated into two or more elements through a chemical reaction.
This is the correct option.
Answer: Endothermic
Explanation:
Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process. Whether a reaction is endothermic or exothermic depends on the difference between the energy needed to break bonds and the energy released when new bonds form.
Answer:
A. -163.96kJ
B. -158.34kJ
Explanation:
Heat of combustion is the heat released when an element with oxygen at stp.
Reaction for the combustion of carbon:
C(s) + O2(g) --> CO2(g)
Enthalpy heat of combustion, C (using Hess law) = -393.5 kJ/mol
m = 5g
Molecular weight = 12 g/mol
No of moles = mass/molecular weight
= 5/12
= 0.417mol
DH = -393.5 * 0.417
= -163.96 kJ
B. Heat absorbed by the calorimeter = heat evolve by combustion
= mCH2ODT + mCcDT
Where CH2O is the specific heat capacity of the water in the calorimeter
Cc is the specific heat capacity of copper calorimeter
= (2500*4.184*14.1) + (2000*0.385*14.1)
= -158343J
= -158.34kJ
