At a certain temperature and pressure, 0.30 mol of carbon dioxide has a
volume of 6.7 L. A 6.7 L sample of hydrogen at the same temperature and
pressure
A) has the same mass
B) contains the same number of atoms
C) has a higher density
D) contains the same number of molecules

Option (D). contains the same number of molecules

Explanation:

From the question given, we obtained the following data:

For CO2:

Number of mole = 0.3mol

Volume = 6.7L

For H2:

Volume = 6.7L

Recall 1mole of a gas occupy 22.4L.

1mol of H2 contains 22.4L

Therefore Xmol of H2 will contain 6.7L i.e

Xmol of H2 = 6.7/22.4 = 0.3mol

Since CO2 and H2 have the same number of mole, they will also contain the same number of molecules.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

the temperature of the gas, in k, not celsius.