Chemistry: Post your doubts here!

[Hamnah Zahoor]

here, can somebody explain me question 16 part (c) ??
the markscheme answer is pentane.

i wasn't able to find even a clue
I guess the question was wrong because as according to the above equation none of the options are correct. Is this a whole question from a paper? if yes please mention the year and variant.
if this is your school exam they might have mixed the question options

 

[FahimJustFahim]

View attachment 64351 Can anyone solve this, please?

its B

View attachment 64351 Can anyone solve this, please?

Its B

 

[tahmed.troy]

X is the oxide of a Period 3 element. X reacts with water to give an acidic solution. A solution is prepared by reacting 0.100g of X with excess water. This solution was neutralised by exactly 25.0 cm of 0.100 mol dm sodium hydroxide solution.
what could be the identity of X?
Al2O3
MgO
P4O10
SO3

 

[ptet.chemistry]

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It is not a fancy channel, but an educational one at best. In my previous work, I was (and still am!) an accomplished synthetic organometallic chemist, working with some of the most air-sensitive compounds. My passion is however in advancing chemical education and affording equal opportunities for all who want to learn from me.

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Cheers.

 

[Zenchin92]

Hi can someone help me with this question ?

 

[ptet.chemistry]

Don't forget to subscribe and share the channel widely with all your friends, chat/study groups, juniors/seniors, teachers, relatives, etc.

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Follow me ptet.chemistry on Instagram, Facebook, and Twitter to get connected. Cheers.

 

[Scoobydoo435]

hi i wanted to ask something relating to electronegativity. In the syllabus it says understand, in simple terms, the concept of electronegativity and apply it to explain the properties of molecules such as bond polarity (see also Section 3.3(c)), the dipole moments of molecules (3.3(d)) and the behaviour of oxides with water. How can i apply the concept to the behaviour of oxides?

More electronegative the central metal atom, more acidic the oxide

 

[blootoomatoo]

P×7000×10*-6=0.96/32×8.31×303


Ans:10.8 kPa

So it's C

Why do you multiply 7000 by 10*-6?

 

[Tasneem Ayham]

Hello Everyone!
Can anyone help me with this? How is it B? How do I solve such equations?

 

[MUGABE King]

OK so first you need to know the reactions of the period 3 oxides with water. AL2O3 does not react so optionA b are wrong. Next we react 2NaOH (which is a basic oxide and the product of reaction between oxide and H2O) with corresponding acidic oxide & balance the equations.
NOTE The Q states"neutralised by exactly 1mol....so D is correct as it balances perfectly with 2NaOH.

thank you

 

[crack the code]

Hello Everyone!
Can anyone help me with this? How is it B? How do I solve such equations?View attachment 66150

what year is this q from?

 

[reinemiraa]

The lattice energies(enthalpies) of rubidium fluoride(RbF) and caesium chloride(CsCl) are -760 KJ/mol and -650kJ/mol respectively. What is the lattice energy of caesium Fluoride(CsF) likely to be? (Rb-37;Cs-55) ANS B
A.-620kJ/mol
B.-720 kJ/mol
C.-800kJ/mol
D.-900kJ/mol
can any1 explain n is this an AS question?

hi , can i know you get B ?

 

[reinemiraa]

The lattice energies(enthalpies) of rubidium fluoride(RbF) and caesium chloride(CsCl) are -760 KJ/mol and -650kJ/mol respectively. What is the lattice energy of caesium Fluoride(CsF) likely to be? (Rb-37;Cs-55) ANS B
A.-620kJ/mol
B.-720 kJ/mol
C.-800kJ/mol
D.-900kJ/mol
can any1 explain n is this an AS question?

do you know the explanation?

 

[reinemiraa]

The lattice energies(enthalpies) of rubidium fluoride(RbF) and caesium chloride(CsCl) are -760 KJ/mol and -650kJ/mol respectively. What is the lattice energy of caesium Fluoride(CsF) likely to be? (Rb-37;Cs-55) ANS B
A.-620kJ/mol
B.-720 kJ/mol
C.-800kJ/mol
D.-900kJ/mol
can any1 explain how the answer is B

 

[astro04]

does anyone know what is the corresponding letters options for questions like this

When organic refuse decomposes in water carboxylic acids are formed. The water becomes acidic and aquatic life is destroyed.
Which additives are suitable to remove this acid pollution?
1 calcium carbonate
2 calcium hydroxide
3 potassium nitrate

The answer is B. Which options is it referring to?

 

[crack the code]

does anyone know what is the corresponding letters options for questions like this

When organic refuse decomposes in water carboxylic acids are formed. The water becomes acidic and aquatic life is destroyed.
Which additives are suitable to remove this acid pollution?
1 calcium carbonate
2 calcium hydroxide
3 potassium nitrate

The answer is B. Which options is it referring to?

option 1 and 2

 

[Samand]

An element X and compound YZ react separately with acid as shown.
X(s) + 2H+(aq) → X2+(aq) + H2(g)
YZ(s) + 2H+(aq) → Y2+(aq) + H2Z(g)
When 1.0 g of either X or YZ is reacted with an excess of acid, the total volume of gas formed is the same.
Which statements are correct?
1. Ar(X) = Mr(YZ)
2. X and Y are metals.
3. X and Y must both be in the same group of the Periodic Table.

Why is the answer "1 and 2 are correct"?

 

[coolhudhayfahfaiz]

Hi guys, I have a question regarding Fe+2 and KMnO4 titrations. So you do know that before carrying out the titration excess dilute sulfuric acid must be added to the Fe+2 solution to allow redox rxn to occur. But doesn't the addition of excess dilute sulfuric acid(mainly water) dilute the Fe+2 solution in the conical flask?

 

[coolhudhayfahfaiz]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

A 20.0mL sample of 0.200M HBr solution is titrated with 0.200M NaOH solution. Calculate the pH of the
solution after the following volumes of base have been added:
15 mL
ANYBODY ????

HBr + NaOH -----> NaBr + H20

n=cv=0.02 x 0.2 = 4 x10^-3 moles of HBr

n of NaOH = cv= 0.015 x 0.2= 3 x 10^-3 moles.

1x10^-3 moles of HBr left. Assuming HBr is a strong acid, [H+] = 1x10^-3/0.02+0.015=0.0286 mol dm^-3

ph=-log[H+]=1.54

 

[crack the code]

Hi guys, I have a question regarding Fe+2 and KMnO4 titrations. So you do know that before carrying out the titration excess dilute sulfuric acid must be added to the Fe+2 solution to allow redox rxn to occur. But doesn't the addition of excess dilute sulfuric acid(mainly water) dilute the Fe+2 solution in the conical flask?

excess dilute acid is added to ensure that the reaction goes to completion only when all of fe2+ ions have been consumed by Mno4- ions and not due to decreased concentration of H+