<span>The question says, in biochemical reactions, enzymes acts as catalyst causing the............. The correct option is A. The minimum energy that must be overcome before a chemical reaction occur is activation energy. Enzymes act as catalyst to lower the activation energy so that the biochemical reaction can occur. </span>
The term defined as the change in direction of light when it goes from one medium into a different medium is refraction.
Refraction is the change of direction on the propagation of a beam of light when it passes from a medium to other; this only happens when the light travels at different speeds in both media.
When a beam of light that travels in the air incedes in a slab of glass, part of the beam is reflected (bounces) and part is refracted (it penetrates in the glass and changes the angle).
Also,due to the different speeds of light in air and water, when a beam of light passes from air to water, it refracts.
1) Reaction
<span>NH4Cl(s) ---> NH3(g) + HCl(g)
2) equilibrium equation, Kc
Kc = [NH3] * [HCl]
3) Table of equilibrium formation
step concentrations
</span>
<span> NH4Cl(s) NH3(g) HCl(g)
start 1.000 mole 0 0
react - x
produce +x + x
------------------ ---------- -----------
end 1 - x +x +x
1 - x = 0.3 => x = 1 - 0.3 = 0.7
[NH3] = [HCl] = 0.7/0.5 liter = 1.4 (I used 0.500 dm^3 = 0.5 liter)
4) Equilibrium equation:
Kc = [NH3] [HCl] = (1.4)^2 = 1.96
Which is the number that you were looking for.
Answer: Kc = 1.96
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The melting of the ice cube indicates physical change has taken place
