Question

1.) Two 100 g pieces of metal, one copper and one aluminum, that start at the same temperature are put in an oven for 2 minutes. When they are taken out of the oven, the copper feels warmer than the aluminum. This can be explained by the relative values of specific heat for the two metals. Copper must have a [ Select ] ["higher", "lower"] specific heat capacity than the aluminum, because [select one: higher heat capacity men a high melting point. OR the molar mass of copper is greater than aluminium, OR the higher heat capacity means a larger temperature change, OR the same quantity of heat resulted in a higher (DELTA) T compared to aluminum. 2.) The molar enthalpy of combustion of methane, CH4 (molar mass of 16.0 g/mol), is 840 kJ/mol.

The molar enthalpy of combustion of ethanol, C2H5OH (molar mass of 46.1 g/mol), is 1360 kJ/mol.

The molar enthalpy of combustion of butane, C4H10 (molar mass of 58.1 g/mol), is 2970 kJ/mol.

What is the correct match for ranking the energy density of these three compounds

Highest energy density

      [ Choose ]            C2H5OH            C4H10            CH4      

Middle energy density

      [ Choose ]            C2H5OH            C4H10            CH4      

Lowest energy density

3.)

A gas has a volume of 115 mL at an initial, unknown pressure. The same sample of gas has a volume of 320 mL at a pressure of 715 torr. What can be said about the initial pressure?

Initial pressure is also equal to 715 torr

Initial pressure is greater than 715 torr

Initial pressure is less than 715 torr

4.)

Isoamyl acetate is the key molecule responsible for the smell of bananas and it has the chemical formula, C7H14O2.

Allyl valerate is a key molecule responsible for the smell of pineapples and it has the chemical formula C8H14O2.

Suppose you are in a very still room (no fans or ventilation system in use to move air around) and a coworker opens vials containing 200 mL samples of gases of each (a) isoamyl acetate and (b) allyl valerate at the same time. If you are standing on the opposite side of the room, which will you smell first and why?

                           [ Select ]                       ["pineapple", "banana"]         because the molecule with the                           [ Select ]                       ["smaller", "larger"]         molar mass diffuses through the air in the room faster.

5.)

Nitroglycerin is a well known explosive. It has a chemical formula of C3H5N3O9 (molar mass is 227.1 g/mol) and when it detonates the balanced equation for the reaction is:

4C3H5N3O9 ----> 6N2 + 12CO2 + 10H2O + O2

If one gram of nitroglycerin gives off 6.260 kJ of energy upon detonation, what is the enthalpy change in the thermochemical equation for this reaction?

4C3H5N3O9 ----> 6N2 + 12CO2 + 10H2O + O2   (DELTA) H = ??

+25.04 kJ

+145.1 kJ

-145.1 kJ

+ 5687 kJ

-25.04 kJ

- 5687 kJ

  

Answer 1

Q1)

ANS

Two 100 g pieces of metal, one copper and one aluminum, that start at the same temperature are put in an oven for 2 minutes. When they are taken out of the oven, the copper feels warmer than the aluminum. This can be explained by the relative values of specific heat for the two metals.

Copper must have a lower specific heat capacity than the aluminum, because the same quantity of heat resulted in a higher (DELTA) T compared to aluminum.

Specific heat capacity is defined as the amount of heat required to raise the temperature of unit gram of a system by 1 degree.

Mathematically it is expressed as S=Q/ ((delta T)*m)

where S is specific heat capacity

Q is the heat supplied to the system

delta T is the corresponding change in temperature

m is the mass of the system under obsservation.

.Also same amount of both copper and aluminium were heated.i.e. 100 g.Since copper becomes more warmer than aluminium.Same amount of heat Q was supplied.

Therefore it can be said that copper has lower specific heat capacity than aluminium because for the same amount of heat supplied the corresponding change in temperature is high as compared to aluminium. Therefore copper feels more warmer than aliminium.