Answer: A catalyst is a substance that speeds up the rate of a chemical reaction without being used up and remains chemically unchanged itself .
Explanation: For a reaction to take place the particles must collide with enough energy for bonds to break and reaction to occur .
BUT when a catalyst is present the reactants are able to react in a way that requires less energy ,leading to more successful collision so the reaction speeds up without the chemical composition of the catalyst being affected
NOTE: the catalyst must be chosen to suit the particular reaction
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Answer:
Samira's model is incorrect because not all atoms are accounted for
Explanation:
The image of Samira's model has been attached to this answer to enhance the explanation.
What is depicted in that model is rightly regarded as a chemical change. In a chemical change atoms of substances are rearranged as new substances are formed.
However, all atoms in the products must also be found in at least one of the reactants. In this case we have an atom in one of the products that is not accounted for. Hence the model is incorrect.
Answer:
[Ni(CN)4]2- square planar
[NiCl4]2- tetrahedral
Explanation:
For a four coordinate complex such as [Ni(CN)4]2- and [NiCl4]2-, we can decide its geometry by closely considering its magnetic properties. Both of the complexes are d8 complexes which could be found either in the tetrahedral or square planar crystal field depending on the nature of the ligand.
CN^- being a strong field ligand leads to the formation of a square planar diamagnetic d8 complex of Ni^2+. Similarly, Cl^- being a weak field ligand leads to the formation a a tetrahedral paramagnetic d8 complex of Ni^+ hence the answer given above.
Answer:
2.343 g/ cm³
Explanation:
Density:
Density is equal to the mass of substance divided by its volume.
Units:
SI unit of density is Kg/m3.
Other units are given below,
g/cm3, g/mL , kg/L
Formula:
D=m/v
D= density
m=mass
V=volume
Symbol:
The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density.
Given data:
density = ?
volume= 350 cm³
mass= 820 g
Now we will put the values in the formula,
d= m/v
d= 820 g/ 350 cm³
d= 2.343 g/ cm³
The density of silicon is 2.343 g/ cm³
