It has 4 significant figures. If you see the Zero after the one decimal point you don’t count that and instead just started at 6
Enthalpy is energy of bonds broken - energy of bonds formed. Here, the NH3 and O2 are broken and H2O and NO are formed. So the energy to break the NH3 bonds is 3 times the amount of energy it takes to break a N-H single bond (because there are three of them in a NH3 molecule) and then multiplied by 4 because there are four particles.
So the energy of the bonds broken is 12x the energy to break a N-H single bond plus 5x the amount of energy to break an O—O double bond (you don’t multiply this by anything because in each O2 molecule there is only one bond).
The energy of the bonds formed is 6*2 = 12 Times the amount of energy for a O-H single bond plus 4 times the amount of energy required to break a N—O double bond.
Subtract energy of bonds broken - energy of bonds formed and this is the change in enthalpy.
To know what type of bond it is, draw the Lewis structure.
Put a thermometer in the water and wait until it boils. When it boils record the temperature and compare it to the normal water boiling point.
1.) 28.0 grams of oxygen
28 grams (1 mole/16 grams per mole)=1.75 moles oxygen
2.)5.0 moles of Iron
5 moles(55.845 grams/1 mole)=279.225 grams Iron
3.) 452 grams Argon
452 grams(1 mole/39.948 grams)=11.315 moles Argon
4.) 16.5 moles Hydrogen
16.5 moles(1.01 grams/1 mole)=16.665 grams Hydrogen
