Answer:
Explanation:
To solve this problem, we must understand the relationship between mass of a substance and the number of atoms.
Atoms are the smallest indivisible particles of any matter. A substance can be made up of several number of atoms in their space.
The mass of any substance is a function of the amount of atoms its contains.
The mass of a substance is related in chemistry to the amount of atoms its contains using the parameter called the number of moles.
A mole is the amount of substance that contains the Avogadro's number of particles. This number is 6.02 x 10²³ particles. The particles here can be protons, neutrons, electrons, atoms e.t.c.
Now,
Number of moles = 
Molar mass of copper = 63.6g/mole
Number of moles = 
= 0.03mole
Since 1 mole of a substance contains 6.02 x 10²³atoms
0.03 mole of copper will contain 0.03 x 6.02 x 10²³atoms
= 1.89 x 10²² atoms
He needs to add 1.89 x 10²² atoms to make 2g of the sample.
Explanation:
It is known that for high concentration of 
, reduction will take place. As, cathode has a positive charge and it will be placed on left hand side.
Now, 
= 0 and the general reaction equation is as follows.
3.00 M n = 2 30 mM
E = 
= 
= 0.038 V
Therefore, we can conclude that voltage shown by the voltmeter is 0.038 V.
The collision of the molecules between the hydrogen molecule or H2, and an iodine molecule or I2, provided there would be a sufficient energy is that the system would eventually undergo a chemical change wherein a new chemical compound would be formed from these two molecules.
117 mL of 0.210 M K₂S solution
Explanation:
The question asks about the volume of 0.210 M K₂S (potassium sulfide) solution required to completely react with 175 mL of 0.140 M Co(NO₃)₂ (cobalt(II) nitrate).
We have the chemical reaction:
K₂S + Co(NO₃)₂ → CoS + 2 KNO₃
molar concentration = number of moles / volume (L)
number of moles = molar concentration × volume
number of moles of Co(NO₃)₂ = 0.140 × 175 = 24.5 mmoles
We see from the chemical reaction that 1 mmole of Co(NO₃)₂ is reacting with 1 mmole of K₂S, so 24.5 mmoles of Co(NO₃)₂ are reacting with 24.5 mmoles of K₂S.
volume = number of moles / molar concentration
volume of K₂S solution = 24.5 / 0.210 = 117 mL
Learn more about:
molar concentration
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