The value of ΔH° for the reaction below is -126 kJ. The amount of heat that is released by the reaction of 40.0 g of Na2O2 with water is kJ. 2Na2O2 (s) + 2H2O (l) → 4NaOH (s) + O2 (g)

-32.3 kJ

Explanation:

Step 1: Write the balanced thermochemical equation

2 Na₂O₂(s) + 2 H₂O(l) ⇒ 4 NaOH(s) + O₂(g)   ΔH° = -126 kJ

Step 2: Calculate the moles corresponding to 40.0 g of Na₂O₂

The molar mass of Na₂O₂ is 77.98 g/mol.

40.0 g × 1 mol/77.98 g = 0.513 mol

Step 3: Calculate the amount of heat released upon the reaction of 0.513 moles of Na₂O₂

According to the thermochemical equation, 126 kJ of heat are released every 2 moles of Na₂O₂.

0.513 mol Na₂O₂ × (-126 kJ/2 mol Na₂O₂) = -32.3 kJ

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

answer by yourhope:

how do models compare to real-world objects?

d. most models represent a real-world object in a simpler way.

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