Question

what is the mass of co2 which contains same no of molecules as are contained in 40 g of oxygen

Answer 1

The molar mass of oxygen is 32g. Thus, there are 6.022 X 1023 molecules of O2 in 32g of O2. 

So

 32g of O2 = 6.022 X 1023 molecules of O2

 1g of O2 = (6.022 X 1023 / 32) molecules of O2  

 40g of O2 = (6.022 X 1023 X 40) / 32 molecules of O2  

 = 7.5275 X 1023 molecules of O2

Thus, there are 7.5275 X 1023 molecules of O2in 40g of O2. Now, the molar mass of carbon dioxide gas (CO2) is 44g. Thus, there are 6.022 X 1023 molecules of CO2 in 44g of CO2. So

 mass of 6.022 X 1023 molecules of CO2 = 44g 

 mass of 1 molecule of CO2 = 44 / (6.023 X 1023) g 

 So, mass of 7.5275 X 1023 molecules of CO2= (44 X 7.5275 X 1023) / (6.022 X 1023) g of CO2

 = 55g of CO2

Answer 2

Hi.

Here is your answer-----

Molecular mass of CO2 = 44 grams

Number of moles of CO2 = mass/ molecular mass
                            = mass/44

Molecular mass of oxygen = 32 grams
mass of oxygen = 40 grams.

number of moles of oxygen = 40/32
      
According to the question,
      Number of moles of CO2 = Number of moles of O2
                                mass/44 = 40/32
                             Mass = 55 grams.

Thus, mass of carbon dioxide is 55 grams.

Hope it will help u.

Have a nice day.