Answer:
0.64 g of S
Solution:
The balance chemical equation is as follow,
2 Cu + S ----> Cu₂S
According to equation,
127 g (2 mole) Cu produces = 159 g (1 mole) of Cu₂S
So,
2.54 g Cu will produce = X g of Cu₂S
Solving for X,
X = (2.54 g * 159 g) / 127 g
X = 3.18 g of Cu₂S
Now, it is confirmed that the reaction is 100% ideal. Therefore,
As,
127 g (2 mole) Cu required = 32 g (1 mole) of S
So,
2.54 g Cu will require = X g of S
Solving for X,
X = (2.54 g * 32 g) / 127 g
X = 0.64 g of S
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.
C. alpha = nucleus of a helium atom
beta = electron
gamma = photon
Answer:
D
Explanation:
The nuclear model of the atom was proposed by Ernest Rutherford.
In his submission, the atom consists of a dense positive nucleus with electrons moving round this nucleus as planets move round the sun. He likened his model to the solar system. The nucleus is at the center of this system just as the sun is at the center of the solar system.
Hydrated salts are when salt crystals have water molecules bound. Anhydrous salts are when the water has been removed.
mass of water removed = hydrated salt - anhydrate salt
= 11.75 g - 9.25 g = 2.50 g
number of water moles = 2.50 g / 18 g/mol = 0.139 mol
number of cobalt (II) chloride moles = 9.25 g / 130 g/mol = 0.0712 mol
ratio of water moles to CoCl₂ moles - 0.139 mol / 0.0712 mol = 1.95
rounded off 2 moles of water for every 1 mol of CoCl₂
formula - CoCl₂.2H₂O
name - Cobalt(II) chloride dihydrate
