Chemistry MCQ thread...

[meoooow]

Read above please meoow i mean :S

yes i did, im sorry, i just joined so its taking me a while to get a hang of this!

Well Welcome to Xpf first of all then

Thankyou!

 

[xHazeMx]

A mixture containing 0.100 mol of CaCO3 and 0.100 mol of CaO are introduced
into an evacuated 0.01 m3 vessel. The vessel is heated to a constant
temperature of 385 K such that the equilibrium below is established.
CaCO3(s) CaO(s) + CO2(g)
The partial pressure of carbon dioxide at equilibrium is then found to be 0.220
atm.
What is the total mass of CaCO3 at equilibrium after an additional 0.300 atm of
carbon dioxide is pumped into the vessel?
A 0.530 g
B 10.0 g
C 12.5 g
D 19.5 g

someone show the calculations for this question

 

[mizmoody]

ryt... how is it D?

 

[meoooow]

3 Equations involving four enthalpy changes are shown.
Na(g) → Na+(g) + e– ΔH = W
Na(g) → Na2+(g) + 2e– ΔH = X
Na(s) → Na(g) ΔH = Y
Na(s) → Na2+(g) + 2e– ΔH = Z

What is the second ionisation energy of sodium?

A 2W B X – W C Y – W D Z – Y

 

[xHazeMx]

ryt... how is it D?

oxygen and the bleach (NaClO) have the same moles
n= 0.0350
v= 0.025 dm3
use C=n/v and u will get the answer as D

 

[xHazeMx]

3 Equations involving four enthalpy changes are shown.
Na(g) → Na+(g) + e– ΔH = W
Na(g) → Na2+(g) + 2e– ΔH = X
Na(s) → Na(g) ΔH = Y
Na(s) → Na2+(g) + 2e– ΔH = Z

What is the second ionisation energy of sodium?

A 2W B X – W C Y – W D Z – Y

X - W ... its B

 

[meoooow]

3 Equations involving four enthalpy changes are shown.
Na(g) → Na+(g) + e– ΔH = W
Na(g) → Na2+(g) + 2e– ΔH = X
Na(s) → Na(g) ΔH = Y
Na(s) → Na2+(g) + 2e– ΔH = Z

What is the second ionisation energy of sodium?

A 2W B X – W C Y – W D Z – Y

X - W ... its B

can you explain? isnt it supposed to be just W? (obv, since there is no option )
but i wana know how it's B.

 

[xHazeMx]

3 Equations involving four enthalpy changes are shown.
Na(g) → Na+(g) + e– ΔH = W
Na(g) → Na2+(g) + 2e– ΔH = X
Na(s) → Na(g) ΔH = Y
Na(s) → Na2+(g) + 2e– ΔH = Z

What is the second ionisation energy of sodium?

A 2W B X – W C Y – W D Z – Y

X - W ... its B

can you explain? isnt it supposed to be just W? (obv, since there is no option )
but i wana know how it's B.

the question is asking about the second ionisation energy only which means the energy required to remove the SECOND electron only. X is the amount of energy required to remove two electrons and W is the energy required to remove one electron. so the energy required to remove the second electron only is X - W
Na(g) → Na2+(g) + 2e– ΔH = X
Na(g) → Na+(g) + e– ΔH = W

Hence, Na+(g) → Na2+(g) + e- ΔH = X - W
hope u got that

 

[meoooow]

12 Camphor is a white solid which was used to make the early plastic celluloid. Camphor contains
the same percentage by mass of hydrogen and oxygen.

What is the molecular formula of camphor?

A C10H6O6 B C10H8O C C10H16O D C10H10O2

can someone show me how to do this?

 

[hassam]

C....mass of H and O in this compound is same....i.e 16 units

 

[xHazeMx]

12 Camphor is a white solid which was used to make the early plastic celluloid. Camphor contains
the same percentage by mass of hydrogen and oxygen.

What is the molecular formula of camphor?

A C10H6O6 B C10H8O C C10H16O D C10H10O2

can someone show me how to do this?

i will tell u how if i m correct. is it C?

 

[xHazeMx]

A mixture containing 0.100 mol of CaCO3 and 0.100 mol of CaO are introduced
into an evacuated 0.01 m3 vessel. The vessel is heated to a constant
temperature of 385 K such that the equilibrium below is established.
CaCO3(s) CaO(s) + CO2(g)
The partial pressure of carbon dioxide at equilibrium is then found to be 0.220
atm.
What is the total mass of CaCO3 at equilibrium after an additional 0.300 atm of
carbon dioxide is pumped into the vessel?
A 0.530 g
B 10.0 g
C 12.5 g
D 19.5 g

it's C but can someone explain it?

 

[Abdulrab]

Q Which compound has a boiling point which is influenced by hydrogen bonding ?

A. CH3CHO
B. CH3OCH3
C. HC02H
D HC02CH3

please explan it to me with answer !!

 

[Zishi]

A mixture containing 0.100 mol of CaCO3 and 0.100 mol of CaO are introduced
into an evacuated 0.01 m3 vessel. The vessel is heated to a constant
temperature of 385 K such that the equilibrium below is established.
CaCO3(s) CaO(s) + CO2(g)
The partial pressure of carbon dioxide at equilibrium is then found to be 0.220
atm.
What is the total mass of CaCO3 at equilibrium after an additional 0.300 atm of
carbon dioxide is pumped into the vessel?
A 0.530 g
B 10.0 g
C 12.5 g
D 19.5 g

it's C but can someone explain it?

The question is now also explained by other user, so I've removed my explanation.

 

[Anonymousx3]

C - HCO2H.

Hydrogen bonding can only occur when an hydrogen atom is directly attached to a small and highly electronegative atom (F, N, O).
In this case, one of the H atoms in the carboxylic acid group is attached to an oxygen atom.

 

[Xthegreat]

Q Which compound has a boiling point which is influenced by hydrogen bonding ?

A. CH3CHO
B. CH3OCH3
C. HC02H
D HC02CH3

please explan it to me with answer !!

answer is C. in C there is a H covalently bonded to an Oxygen atom, hence, hydrogen bonds can form.

H bonds are formed when H is covalently bonded to F/O/N atoms. read up on hydrogen bondings.

 

[Abdulrab]

but in A also oxygen is attached to hydrogen !!

 

[MHHaider707]

A mixture containing 0.100 mol of CaCO3 and 0.100 mol of CaO are introduced
into an evacuated 0.01 m3 vessel. The vessel is heated to a constant
temperature of 385 K such that the equilibrium below is established.
CaCO3(s) CaO(s) + CO2(g)
The partial pressure of carbon dioxide at equilibrium is then found to be 0.220
atm.
What is the total mass of CaCO3 at equilibrium after an additional 0.300 atm of
carbon dioxide is pumped into the vessel?
A 0.530 g
B 10.0 g
C 12.5 g
D 19.5 g

it's C but can someone explain it?

At equilibrium pressure of CO2 is 0.22 atm i-e (0.22x1x10^5) Pa

Using PV = nRT calculate the moles of CO2 present at equilibrium and it will be 0.0688 mol....

Initial concentration of CaCO3 was 0.1 mol so calculate the molar conc. of CaCO3 at equilibrium and it will be 0.312 mol...


Now when additional 0.3 atm CO2 is introduced equilibrium will shift to left and CaCO3 will be produced by this additional moles of CO2....

Calculate the molar conc. of CO2 which is added by PV = nRT

moles of CaCO3 will be now 0.312 + 0.0938 = 0.125 mol

calculate the mass of CaCO3 by Mass = Moles x Mr

and it is 12.5 g so ans. is C!!!

 

[Anonymousx3]

but in A also oxygen is attached to hydrogen !!

No, it isn't.
It's an aldehyde, the oxygen is double bonded to the carbon atom, it has no more available bonds for the hydrogen.
The hydrogen is attached to the carbon.

 

[hassam]

Which of the following statement(s) is/are true?
1 When SiCl4 is added to water, a precipitate is formed.
2 sulfur has a higher melting point than phosphorus because the intermolecular
attractions are stronger.
3 When AlCl3 is dissolved in water, [Al(H2O)5(OH)]2+(aq) is one of the ions
formed.