Chemistry MCQ thread...

[Xthegreat]

2 Use of the Data Booklet is relevant to this question.
A typical solid fertiliser for use with household plants and shrubs contains the elements N, P, and
K in the ratio of 15 g : 30 g :15 g per 100 g of fertiliser. The recommended usage of fertiliser is 14 g
of fertiliser per 5 dm3 of water.
What is the concentration of nitrogen atoms in this solution?
A 0.03 mol dm–3
B 0.05 mol dm–3
C 0.42 mol dm–3
D 0.75 mol dm–3

can anyone help me with it???? plz

Ans : A
- the percentage of N is the fertiliser is 15/100 = 0.15%
- in 14g of fertiliser, the amount of N is 14 x 0.15 = 2.1g
- the number of moles of N is 2.1g of N is 2.1/14 = 0.15 mole
- concentration = mole/volume, hence, 0.15/5 = 0.03moldm-3

right?

 

[MHHaider707]

Which of the following statements is true about hydrogen halides?
A Enthalpy change of formation becomes less exothermic down the group.
B Thermal stability increases down the group.
C Acidity of the corresponding aqueous solution decreases down the group.
D Charge density of cation decreases down the group.
Astatine is below iodine in Group VII.
Which of the following would be a correct prediction for astatine and its compounds?
A Astatine would oxidise chloride to chlorine.
B Potassium astatide would be a white crystalline solid.
C Astatine is insoluble in chloroform.
D Silver astatide reacts with concentrated aqueous ammonia to form a soluble complex.

D for the first one n C for the next.....rite???

 

[xHazeMx]

Which of the following statements is true about hydrogen halides?
A Enthalpy change of formation becomes less exothermic down the group.
B Thermal stability increases down the group.
C Acidity of the corresponding aqueous solution decreases down the group.
D Charge density of cation decreases down the group.
Astatine is below iodine in Group VII.
Which of the following would be a correct prediction for astatine and its compounds?
A Astatine would oxidise chloride to chlorine.
B Potassium astatide would be a white crystalline solid.
C Astatine is insoluble in chloroform.
D Silver astatide reacts with concentrated aqueous ammonia to form a soluble complex.

both are A right ?

 

[Zishi]

Which of the following statements is true about hydrogen halides?
A Enthalpy change of formation becomes less exothermic down the group.
B Thermal stability increases down the group.
C Acidity of the corresponding aqueous solution decreases down the group.
D Charge density of cation decreases down the group.

D

Astatine is below iodine in Group VII.
Which of the following would be a correct prediction for astatine and its compounds?
A Astatine would oxidise chloride to chlorine.
B Potassium astatide would be a white crystalline solid.
C Astatine is insoluble in chloroform.
D Silver astatide reacts with concentrated aqueous ammonia to form a soluble complex.

B

 

[hassam]

WAT WUD BE OXIDATION NO. OF IODINE IN IBr

 

[hassam]

1st one is A....2nd one b so zishi got 1 rong

 

[abdullah181994]

IS THERE HYDROGEN BONDING IN ALDEHYDE

 

[xHazeMx]

WAT WUD BE OXIDATION NO. OF IODINE IN IBr

i think -1 because Br is less electronegative

 

[abdullah181994]

PLEASE ANSWER MY QUESTION ON PREVIOUS PAGE

 

[abdullah181994]

WAT WUD BE OXIDATION NO. OF IODINE IN IBr

i think -1 because Br is less electronegative

BR IS MORE ELECTRONEGATIVE ITS +1

 

[Zishi]

1st one is A....2nd one b so zishi got 1 rong

Is ever enthalpy change of formation of HI exothermic? IT IS endothermic.

Charge density: -ve charge/volume

As negative charge decreases down the group and volume increases, so charge density has to decrease. Let me confirm it...

 

[Zishi]

WAT WUD BE OXIDATION NO. OF IODINE IN IBr

+1

 

[xHazeMx]

WAT WUD BE OXIDATION NO. OF IODINE IN IBr

i think -1 because Br is less electronegative

BR IS MORE ELECTRONEGATIVE ITS +1

yeah correct i think i should sleep too

 

[Xthegreat]

Which of the following statements is true about hydrogen halides?
A Enthalpy change of formation becomes less exothermic down the group.
B Thermal stability increases down the group.
C Acidity of the corresponding aqueous solution decreases down the group.
D Charge density of cation decreases down the group.

D

* shouldn't the answer for this be A? i though the cation is the same throughout the group? H+ right?

 

[xHazeMx]

Which of the following statements is true about hydrogen halides?
A Enthalpy change of formation becomes less exothermic down the group.
B Thermal stability increases down the group.
C Acidity of the corresponding aqueous solution decreases down the group.
D Charge density of cation decreases down the group.

D

* shouldn't the answer for this be A? i though the cation is the same throughout the group? H+ right?

yeah, the answer is A

 

[Xthegreat]

1st one is A....2nd one b so zishi got 1 rong

Is ever enthalpy change of formation of HI exothermic? IT IS endothermic.

Charge density: -ve charge/volume

As negative charge decreases down the group and volume increases, so charge density has to decrease. Let me confirm it...

formation
1/2H2 + 1/2I2 -> HI
bond energy = broken - formed
= ( 218 + 75.5) - ( 299)
= -5.5 EXOTHERMIC!!!

 

[Zishi]

yeah, the answer is A

Oh, really annoying of me...I read the question as charge density of anion. Dammit. :bad:

 

[Zishi]

1st one is A....2nd one b so zishi got 1 rong

Is ever enthalpy change of formation of HI exothermic? IT IS endothermic.

Charge density: -ve charge/volume

As negative charge decreases down the group and volume increases, so charge density has to decrease. Let me confirm it...

formation
1/2H2 + 1/2I2 -> HI
bond energy = broken - formed
= ( 218 + 75.5) - ( 299)
= -5.5 EXOTHERMIC!!!

Then I guess I shouldn't reply on CIE endorsed book - in it it is given as +11kJmol^-1

 

[Zishi]

1st one is A....2nd one b so zishi got 1 rong

Is ever enthalpy change of formation of HI exothermic? IT IS endothermic.

Charge density: -ve charge/volume

As negative charge decreases down the group and volume increases, so charge density has to decrease. Let me confirm it...

formation
1/2H2 + 1/2I2 -> HI
bond energy = broken - formed
= ( 218 + 75.5) - ( 299)
= -5.5 EXOTHERMIC!!!

Well, it IS ENDOTHERMIC...See wikipedia: http://en.wikipedia.org/wiki/Standard_e ... a_table%29

 

[abdullah181994]

PLZ PLZ PLZ PLZ PLZ ANSWER THIS