Answer:
d and e - Sodium and antimony
Explanation:
The atomic numbers remain the same, while the mass numbers change (because neutrons are being added or taken away).
sodium has an atomic number of 19 and a mass number of 39 - in d, it has an atomic number of 19 but a mass number of 40. therefore, it is an isotope
antimony has an atomic number of 51 and a mass number of 121.60 - in e, it has an atomic number of 51, but a mass number of 123. therefore, it is an isotope
Answer: Th enthalpy of combustion for the given reaction is 594.244 kJ/mol
Explanation: Enthalpy of combustion is defined as the decomposition of a substance in the presence of oxygen gas.
W are given a chemical reaction:



To calculate the enthalpy change, we use the formula:

This is the amount of energy released when 0.1326 grams of sample was burned.
So, energy released when 1 gram of sample was burned is = 
Energy 1 mole of magnesium is being combusted, so to calculate the energy released when 1 mole of magnesium ( that is 24 g/mol of magnesium) is being combusted will be:

kilo 103 is the correct answer so it would mostly be 2
Answer : Option A) HF.
Explanation : Assuming the complete question as per the attachment.
H-F bonds are formed because of hydrogen bonding between H atom and F atom and is considered to be strongest amongst the rest other options given.
As given in the table it is clear that the molar mass of HF molecule is the lowest. It shows that, when dispersion increases in the molecule molecular weight also increases.
Answer:
it is equal to 125 kPa
Explanation:
move the decimal 3 to the left