Answer: 404.04 kJ.
Explanation:
To calculate the moles, we use the equation:
moles of

According to stoichiometry :
2 moles of
on burning produces = 1036 kJ
Thus 0.78 moles of
on burning produces =
Thus the enthalpy change when burning 26.7 g of hydrogen sulfide is 404.04 kJ.
Answer:
number of moles = 0.21120811
Explanation:
To find the number of moles, given the mass of the solute, we use the formula:




Label the variables with the numbers in the problem:



The first thing we have to do is find the molar mass of sodium sulfate, in order for us to use the formula for finding the number of moles:
Formula for finding the molar mass of sodium sulfate:

For the variables and what they mean are below for finding the molar mass of sodium sulfate:





Plug the numbers into the formula, to find the molar mass of sodium sulfate:











Now that we have found the molar mass, we can calculate the number of moles in the solution of sodium sulfate with the formula:








0.21120811 rounded gives you 0.2112
or if you did the problem without decimals
30 grams of sodium sulfate divided by its molecular weight – which we found to be 142 – gives us a value of 0.2113 moles.
Thomson's model of the atom was called the plum pudding model. He discovered electrons, so he placed them in the atoms. This was before the nucleus was discovered.
Now, the current model is an atom that contains a positively charged nucleus (with both protons and neutrons), and negatively charged orbitals with electrons.