Chemistry: Post your doubts here!

[MShaheerUddin]

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).

Bro what this 1 represent in ratio "1"/0.174

 

[MShaheerUddin]

Corona
Bro Can You tell me How can element Calcium have giant structure?

 

[corona]

Bro what this 1 represent in ratio "1"/0.174

The question asks for the ratio of masses of Gas X to Gas Y, but 0.174 is the ratio of masses of Gas Y to Gas X.
Hence, we reciprocate it.

 

[corona]

Corona
Bro Can You tell me How can element Calcium have giant structure?

Metals generally are, on an atomic scale, giant structures in which electrons in the outer shells of the metal atoms are free to move.

Edit:
Reference: https://www.chemguide.co.uk/atoms/structures/metals.html

 

[MShaheerUddin]

OMG Thanks!

 

[MShaheerUddin]

 

[Metanoia]

View attachment 62979

50 cm^3 of CH4 will react with 100 cm^3 of oxygen to produce 50 cm^3 of CO2 and water

Immediately after the reaction, we will have mixture of 50 cm^3 of CO2 and 50 cm^3 of O2 (excess unreacted)

The acidic CO2 would be absorbed by the KOH (alkali) leaving only 50 cm^3 of O2 in the tube

 

[Unknown202]

Can someone explain wht is meant by
34 Which statements correctly describe an effect of a rise in temperature on a gas-phase reaction?
1 More particles now have energies greater than the activation energy.
2 The energy distribution profile changes with more particles having the most probable energy.
3 The activation energy of the reaction is decreased.
The one marked in red ik the answer is 1 but I want to understand 2 plzz help

 

[Unknown202]

Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.
N2(g) + 3H2(g) 2NH3(g) ∆H –ve
What will increase the rate of the forward reaction?
A adding argon to the mixture but keeping the total volume constant
B decreasing the temperature
C increasing the total pressure by reducing the total volume at constant temperature
D removing ammonia as it is made but keeping the total volume of the mixture the same
And these one B and C both seem correct ?!

 

[Prasannadhungel4]

can we carry forward our winter 2017 chemistry grades to next winter 2018.

 

[Hamnah Zahoor]

B decreasing the temperature

This will favour the forward reaction but will not increase the rate...less energy in reacting particles.

 

[studyingrobot457]

can we carry forward our winter 2017 chemistry grades to next winter 2018.

yes,https://help.cambridgeinternational...-be-carried-forward-within-a-13-month-period-

 

[RockstarRifat]

9701/12/O/N/15 Q-39
I am not able to understand how to figure out whether one or many products are formed?

 

[Hamnah Zahoor]

The energy distribution profile changes with more particles having the most probable energy.

Energy distribution profile refers to the profile showing the ethalpy change of a reaction and Activation energy of the reaction ...increasing the temperature will not effect it both will remain the same ......the statement is a bit confusing though.

 

[Metanoia]

Can someone explain wht is meant by
34 Which statements correctly describe an effect of a rise in temperature on a gas-phase reaction?
1 More particles now have energies greater than the activation energy.
2 The energy distribution profile changes with more particles having the most probable energy.
3 The activation energy of the reaction is decreased.
The one marked in red ik the answer is 1 but I want to understand 2 plzz help

The 'most probable energies' at a specific temperatures are the respective peaks
When temperature increases, the peak is lowered, thus less particles will have the most probable energy

 

[Prometheus Gomes]

9701_s13_qp12 question 21,24,25,26

 

[Bhuvana123]

Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.
N2(g) + 3H2(g) 2NH3(g) ∆H –ve
What will increase the rate of the forward reaction?
A adding argon to the mixture but keeping the total volume constant
B decreasing the temperature
C increasing the total pressure by reducing the total volume at constant temperature
D removing ammonia as it is made but keeping the total volume of the mixture the same
And these one B and C both seem correct ?!

The answer is B because the forward reaction is exothermic and a decrease in temperature will favor the forward reaction. if there is an increase in temperature it will favor the reverse reaction which is endothermic.

 

[Bhuvana123]

View attachment 62954
someone plz solve these question answer is A

Hey please tell me if you get the answer

 

[Unknown202]

This will favour the forward reaction but will not increase the rate...less energy in reacting particles.

So doesn't it if to be C

 

[Unknown202]

all ASmoles questions solved

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

Hey please tell me if you get the answer