Chemistry Problems for 9 – 14 – 16

 

Problem 1

Which sample of matter sublimes at room temperature and standard pressure?
(1) Br2()
(2) Cl2(g)
(3) CO2(s)
(4) SO2(aq)

¿Qué muestra de materia realiza sublimación a temperatura ambiente y presión estándar?
(1) Br2(ℓ)
(2) Cl2(g)
(3) CO2(s)
(4) SO2(aq)

Discussion and Solution:
The term sublime refers to when a substance goes from the solid state to the gaseous state without going through the liquid state.
The only solid substance listed is in choice (3).
By The Way, solid carbon dioxide gas is usually referred to as dry ice.

Problem 2

Which reaction occurs at the cathode in an electrochemical cell?
(1) combustion
(2) neutralization
(3) oxidation
(4) reduction

¿Qué reacción ocurre en el cátodo en una celda electroquímica?
(1) combustión
(2) neutralización
(3) oxidación
(4) reducción

Discussion and Solution:
Remember the adage, An Ox, Red Cat?
At the Anode, Oxidation occurs.
Reduction occurs at the Cathode.
Choice (4).

Problem 3

Which substance yields H+(aq) as the only positive ion in an aqueous solution?
(1) CH3CHO
(2) CH3CH2OH
(3) CH3COOH
(4) CH3OCH3

¿Qué sustancia cede H+(aq) como el único ion positivo en una solución acuosa?
(1) CH3CHO
(2) CH3CH2OH
(3) CH3COOH
(4) CH3OCH3

Discussion and Solution:
Only acids release H+ ions in aqueous solution.
The only acid listed is choice (3).
Choice (1) is an aldehyde.
Choice (2) is an alcohol.
Choice (4) is a ketone.

Problem 4

During a nuclear reaction, mass is converted into
(1) charge
(2) energy
(3) isomers
(4) volume

Durante una reacción nuclear, la masa se convierte en
(1) carga
(2) energía
(3) isómeros
(4) volumen

Discussion and Solution:
According to Einstein’s Equation, E = mc2, mass is converted into energy.
Choice (2).

Problem 5

An atom in the ground state has two electrons in its first shell and six electrons in its second shell. What is the total number of protons in the nucleus of this atom?
(1) 5
(2) 2
(3) 7
(4) 8

Un átomo en estado fundamental tiene dos electrones en su primera capa y seis electrones en su segunda capa. ¿Cuál es el número total de protones en el núcleo de este átomo?
(1) 5
(2) 2
(3) 7
(4) 8

Discussion and Solution:
Since the atom is in the ground state, all the electrons are where they are supposed to be.
With a total of eight electrons, in order for the atom to be neutral, it must have eight protons.
Choice (4).

 

 

 

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