Chemistry: Post your doubts here!

[Ayesha Amjad 22]

Hi Everyone I would like to post some very inportant notes for cie AS Level Chemistry. Download the notepad file. It contains the link to the website for Chemistry notes AS Levels only

 

[achaaa]

Question 2 b(iii)

 

[Unknown202]

someone plz solve these question answer is A

 

[Unknown202]

why ans is B plzzzzzzzzzz help

 

[Unknown202]

and this answer is A why?

 

[allexaa99]

View attachment 62955
why ans is B plzzzzzzzzzz help

First, you write out the equation

2C3H7OH(l) + 9O2(g) -> 6CO2(g) + 8H2O(l)

0.1 mol of propanol = 2.4dm3

From the equation:
2mol of propanol reacts with 9mol of oxygen
0.1mol of propanol reacts with 0.45mol of oxygen

0.45mol of oxygen=10.8dm3

After the reaction,
Since we have 12dm3 of oxygen (excess), there will be 1.2dm3 of oxygen left.
7.2dm3 of carbon dioxide will be produced from the reaction.

1.2+7.2=8.4dm3

 

[fahadhameedahmad]

View attachment 62954
someone plz solve these question answer is A

all AS moles questions solved

Moles & Stoichiometry : Past Paper Questions (9701 AS Chemistry MCQs): https://www.youtube.com/playlist?list=PL0U7Zwed3btQLUSSG9QtGUry32Q1D-_xU

 

[fahadhameedahmad]

View attachment 62955
why ans is B plzzzzzzzzzz help

all moles past paper questions solved

Moles & Stoichiometry : Past Paper Questions (9701 AS Chemistry MCQs): https://www.youtube.com/playlist?list=PL0U7Zwed3btQLUSSG9QtGUry32Q1D-_xU

 

[MShaheerUddin]

Help please.

 

[fahadhameedahmad]

View attachment 62954
someone plz solve these question answer is A

 

[fahadhameedahmad]

View attachment 62955
why ans is B plzzzzzzzzzz help

 

[MShaheerUddin]

Sir please answer my one.

 

[Unknown202]

Sir ur video are soo useful but if u can write for each question the year and paper at the title of the video rather than than at the description cuz it takes time to open each and every video to find the question u want plzz sir

 

[fahadhameedahmad]

i will change the format, question number + year in the title
like this

 

[Unknown202]

Yea but if u can also add no.of question not only year and qp plzzzz

 

[fahadhameedahmad]

yes, the question number would be given at the start

 

[corona]

Help please.

The answer is C.

Boron trifluoride is trigonal planar because Boron has 3 valence electrons, while the nitrogen compound is tetrahedral because nitrogen has 5 electrons and only 3 were used for bonding, leaving a pair of unbonded electrons.

The compounds form a coordinate bond after reacting, where both the electrons from the nitrogen atom are used in forming the bond. Hence, the configuration for both sections is tetrahedral.

 

[MShaheerUddin]

 

[MShaheerUddin]

 

[corona]

View attachment 62975

The answer is A.

2Mg(NO3)2 ------> 2MgO + 4NO2 + O2

The ratio of number of moles of NO2 (gas X) and O2 (gas Y) is 4:1

molar masses:
X - 46
Y - 32

mass = (relative) number of moles * molar mass

X - 46*4 = 184
Y - 32*1 = 32

32/184 = 0.174

Hence, the ratio of masses is 1/0.174 (A).