Chemistry: Post your doubts here!

[studentagakhan]

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 25.0cm3 of 0.100moldm–3 sodium hydroxide solution. What could be the identity of X?
A. Al 2O3
B. MgO
C. P4O10
D. SO3

 

[Laibaaa]

Q.25 anyone please reply soonn

 

[Thought blocker]

7. Use of the Data Booklet is relevant for this question. In an experiment, the burning of 1.45g (0.025mol) of propanone was used to heat 100g of water. The initial temperature of the water was 20.0°C and the final temperature of the water was 78.0°C. Which experimental value for the enthalpy change of combustion for propanone can be calculated from these results? A –1304kJ mol–1 B –970kJ mol–1 C –352kJ mol–1 D –24.2kJ mol

B?

 

[Thought blocker]

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 25.0cm3 of 0.100moldm–3 sodium hydroxide solution. What could be the identity of X?
A. Al 2O3
B. MgO
C. P4O10
D. SO3

D?

 

[Thought blocker]

Q.25 anyone please reply soonn

B?

 

[Lostsoul]

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Every topic in CIE A2, perfectly set in chronological order for your understanding.

You guys should check it out! And Subscribe

 

[sharjilali90]

A2 chemistry O/N 11, variant 43
"Calculate the pH of the buffer formed when 10.0 cm3 of 0.100 mol dm–3 NaOH is added to 10.0 cm3 of 0.250 mol dm–3 CH3CO2H, whose pKa = 4.76"
How do I solve this?

 

[Thought blocker]

A2 chemistry O/N 11, variant 43
"Calculate the pH of the buffer formed when 10.0 cm3 of 0.100 mol dm–3 NaOH is added to 10.0 cm3 of 0.250 mol dm–3 CH3CO2H, whose pKa = 4.76"
How do I solve this?
View attachment 61150

https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-371#post-736866

 

[drowning-in-studies]

36 Ammonia and chlorine react in the gas phase.
8NH3 + 3Cl 2 → N2 + 6NH4Cl
Which statements are correct?
1 Ammonia behaves as a reducing agent.
2 Ammonia behaves as a base.
3 The oxidation number of the hydrogen changes.
The answer is B
I don't understand why 3 is false. Doesn't H change from +3 to +4??

 

[Thought blocker]

36 Ammonia and chlorine react in the gas phase.
8NH3 + 3Cl 2 → N2 + 6NH4Cl
Which statements are correct?
1 Ammonia behaves as a reducing agent.
2 Ammonia behaves as a base.
3 The oxidation number of the hydrogen changes.
The answer is B
I don't understand why 3 is false. Doesn't H change from +3 to +4??

oxidation number of hydrogen is +1.
There are 3 hydrogen molecules so we multiply 3 with +1 and so with 4 molecules of hydrogen 4(+1)
So oxidation number is unchanged of hydrogen

 

[drowning-in-studies]

oxidation number of hydrogen is +1.
There are 3 hydrogen molecules so we multiply 3 with +1 and so with 4 molecules of hydrogen 4(+1)
So oxidation number is unchanged of hydrogen

Ahh...I see Thanks

 

[kungfuPanda]

Hi guys Ive simple question,Are we allowed to explain terms like e.g orbital hybridization or something like this ..I mean definitions?
Will we be awarded marks or no marks if we explain or not explain definitions?

2nd quetsion is are marks only awarded for what a question seeks in terms of our broad understanding or are they predefined and restricted in the marks sheets? like award this 1 marks and award this 2 marks or one or whatever?
linkinpark help me out bro

 

[Thought blocker]

Hi guys Ive simple question,Are we allowed to explain terms like e.g orbital hybridization or something like this ..I mean definitions?
Will we be awarded marks or no marks if we explain or not explain definitions?

2nd quetsion is are marks only awarded for what a question seeks in terms of our broad understanding or are they predefined and restricted in the marks sheets? like award this 1 marks and award this 2 marks or one or whatever?
linkinpark help me out bro

If u are learning CIE, till I know, i didnt come across any different things, may be if u learned some other board and appearing CIE A levels, till i know they do accept, as this is what sir said to me, thought its not in ms, but answers equivallent is considered.

Wait for others to reply u.

 

[kungfuPanda]

If u are learning CIE, till I know, i didnt come across any different things, may be if u learned some other board and appearing CIE A levels, till i know they do accept, as this is what sir said to me, thought its not in ms, but answers equivallent is considered.

Wait for others to reply u.

Yup Cie it is,btw dudee this site is totally dead :3

 

[drowning-in-studies]

How do you solve this?? Do you just add?
Can someone pls explain each statement?
The ans is D

 

[Thought blocker]

Yup Cie it is,btw dudee this site is totally dead :3

Agreed!

 

[Thought blocker]

How do you solve this?? Do you just add?
Can someone pls explain each statement?
The ans is D

Just follow the direction.
1. U to S + S to R = U to R = -92 + 134 = 42
2. T to S = T to U + U to S = -75 - 92 = exothermic.
3. R to T = R to S + S to U + U to T = -134 + 92 + 75 = 33.

Only 1 is correct. THus D.

 

[drowning-in-studies]

Just follow the direction.
1. U to S + S to R = U to R = -92 + 134 = 42
2. T to S = T to U + U to S = -75 - 92 = exothermic.
3. R to T = R to S + S to U + U to T = -134 + 92 + 75 = 33.

Only 1 is correct. THus D.

But how do you decide when to add and subtract? Is it in reference to where the arrows are pointing? What am i missing out?
like, -75+92 or -75-92?

 

[Thought blocker]

But how do you decide when to add and subtract? Is it in reference to where the arrows are pointing? What am i missing out?
like, -75+92 or -75-92?

Yes by looking at arrow.
It took 92 energy from s to u, so -92 from u to s. Get it?

 

[Bah...]

Hello, can somebody please help me solve these questions?







Thanks in advance.