Question:
What's the article about?
 
        
             
        
        
        
A spring - also an electromagnet. Also know as a slinky!
 
        
                    
             
        
        
        
Look at the periodic table to find the charge on atoms. 
 Magnesium is +2 and Nitrogen is -3. Since there are two nitrogen charge 2*-3 = -6 there needs to be 3 Mg then (3*2+ = 6+) to pair with the two nitrogen. 
3 Mg(+2) + 2 N(-3) = Mg3N2 
        
                    
             
        
        
        
Answer:
w = -531 kJ
1. Work was done by the system.
Explanation:
Step 1: Given data
- Heat gained by the system (q): 687 kJ (By convention, when the system absorbs heat, q > 0).
- Change in the internal energy of the system (ΔU°): 156 kJ
Step 2: Calculate the work done (w)
We will use the following expression.
ΔU° = q + w
w = ΔU° - q
w = 156 kJ - 687 kJ
w = -531 kJ
By convention, when w < 0, work is done by the system on the surroundings.
 
        
             
        
        
        
<em>m Na₂CO₃: 23g×2 + 12g + 16g×3 = 106 g/mol</em>
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1 mol ------- 106g 
X ------------ 10,6g
X = 10,6/106
<u>X = 0,1 mol Na₂CO₃</u>