A substance that has no specific volume changes to a substance that has a specific volume.
Answer:
The forward reaction is exothermic.
Explanation:
- Le Châtelier's principle states that when there is an dynamic equilibrium, and this equilibrium is disturbed by an external factor, the equilibrium will be shifted in the direction that can cancel the effect of the external factor to reattain the equilibrium.
- When the mixture turned darker brown, this means that the reaction is shifted towards the left direction (reactants side).
- The temperature is increased and the reaction shifted to the reverse direction, this means that the forward direction is exothermic.
- Exothermic reaction releases heat and when increasing the temperature, the reaction will be shifted to the reverse direction to suppress the effect of increasing the temperature.
- <em>So the right choice is: The forward reaction is exothermic. </em>
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Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
Thus in the reactants, there are 2 atoms of hydrogen and 2 atoms of iodine .Thus there has to be 2 atoms of hydrogen and 2 atoms of iodine in the product as well. Thus a coefficient of 2 is placed in front of HI.
The balanced chemical reaction is:

Answer:
a. The second run will be faster.
d. The second run has twice the surface area.
Explanation:
The rate of a reaction is proportional to the surface area of a catalyst. Given the volume (V) of a sphere, we can find its surface area (A) using the following expression.

The area of the 10.0 cm³-sphere is:

The area of each 1.25 cm³-sphere is:

The total area of the 8 1.25cm³-spheres is 8 × 5.61 cm² = 44.9 cm²
The ratio of 8 1.25cm³-sphere to 10.0 cm³-sphere is 44.9 cm²/22.4 cm² = 2.00
Since the surface area is doubled, the second run will be faster.