سؤال ضروري chemistry

Salamou3alaikoum,
Please i need help with this problem because i have to submit it tommoro morning


In this lab, you will conduct two such investigations. In the first one we will examine the combustion of magnesium. The burning of magnesium can be represented by the equation:
Mg(s) + ½O2(g) ----> MgO(s)
This equation can be obtained by manipulating the three reactions shown below:
(1) MgO(s) + 2 HCl(aq) ----> MgCl2(aq) + H2O
(2) Mg(s) + 2 HCl(aq) -----> MgCl2(aq) + H2(g)
(3) H2(g) + ½O2(g) ---------> H2O(l)

We did an experiment for reactions 1 and 2, with mass of Mg= 0.21g, initial temperature:
23C, Final temp: 33C; and mass MgO=0.64g, Initial temp:23C, Final temp: 28C

How would you find the molar enthalpy of combustion of magnesium
when i did it i got a value of about -20 kJ/mol; however this is very low compared to the accepted value which is -601.6 KJ/mol

http://www2.ucdsb.on.ca/tiss/stretto...2/enthlab3.htm

استعيني بهادا اللينك بيشرح التجربة loi de Hess و بيعطيك الخطوات يلي لازم تتبعيها لتحديد ال DH تبع ال Rx ...
في معطيات لازم ترجعيلها من ال brochure تبعيت ال manipulation .
وبما انها تجربة مختبر قد يطلع معك جواب غلط [بعيد عن المطلوب] و هادا بيرجع لأخطاء خلال التجربة داخل المختبر[خطأ قياس ، أو قراءة أو ....].

Thank you very much