Answer:
Na₂CO₃.2H₂O
Explanation:
For the hydrated compound, let us denote is by Na₂CO₃.xH₂O
The unknown is the value of x which is the amount of water of crystallisation.
Given values:
Starting mass of hydrate i.e Na₂CO₃.xH₂O = 4.31g
Mass after heating (Na₂CO₃) = 3.22g
Mass of the water of crystallisation = (4.31-3.22)g = 1.09g
To determine the integer x, we find the number of moles of the anhydrous Na₂CO₃ and that of the water of crystallisation:
Number of moles = 
Molar mass of Na₂CO₃ =[(23x2) + 12 + (16x3)] = 106gmol⁻¹
Molar mass of H₂O = [(1x2) + (16)] = 18gmol⁻¹
Number of moles of Na₂CO₃ = 
= 0.03mole
Number of moles of H₂O = 
= 0.06mole
From the obtained number of moles:
Na₂CO₃ H₂O
0.03 0.06
Simplest
Ratio 0.03/0.03 0.03/0.06
1 2
Therefore, x = 2
Answer:
44 g
Explanation:
The formula for the number of moles (n) is equal to 
.
Since we need to find the mass, we derive it from the formula of the number of moles and we get that mass = n x molecular weight .
The molecular weight of 
= 12 g/mol (from the carbon) + 19x4 g/mol (from the 4 fluorine atoms)= 88 g/mol
We plug in the numbers in the derived formula for the mass and we get :
mass = n x molecular weight = 0.5 mol x 88 g/mol = 44 g
Ionic bond is formed due to the transfer of electrons from one atom to another so that all atoms involved in the bond would become stable (with 8 electrons in the outermost level)
Now, for bromine, it has 35 electrons. This means that bromine has 7 valence electrons in the outermost level. Therefore, bromine needs to gain one electron in order to become stable.
Bromine can react with elements from:
group 1: each element in group 1 needs to lose one electron to become stable. Therefore, one bromine atom can form an ionic bond when combined with an atom of an element from group 1 (element in group 1 loses its electron for bromine atom).
group 2: each element in group 2 needs to lose two electrons to become stable. Therefore, two bromine atoms can form ionic bonds when combined with an atom of an element from group 2 (element in group 2 loses two electrons, one for each bromine atom).
group 3: each element in group 3 needs to lose three electrons to become stable. Therefore, three bromine atoms can form ionic bonds when combined with an atom of an element from group 1 (element in group 3 loses three electrons, one for each bromine atom).
Since no choices are given , I cannot tell the exact choice. But the correct one would be the element from either group 1 , 2 or 3.
Answer:
108.9g of Silver can be produced from 125g of Ag2S
Explanation:
The compound Ag2S shows that two atoms of Silver Ag, combined with an atom of Sulphur S to form Ag2S. We can as well say the combination ration of Silver to Sulphur is 2:1
•Now we need to calculate the molecular weight of this compound by summing up the molar masses of each element in the compound.
•Molar mass of Silver Ag= 107.9g/mol
•Molar mass of Sulphur S= 32g/mol
•Molecular weight of Ag2S= (2×107.9g/mol) + 32g/mol
•Molecular weight of Ag2S= 215.8g/mol + 32g/mol= 247.8g/mol
•From our calculations, we know that 215.8g/mol of Ag is present in 247.8g/mol of Ag2S
If 247.8g Ag2S produced 215.8g Ag
125g Ag2S will produce xg Ag
cross multiplying we have
xg= 215.8g × 125g / 247.8g
xg= 26975g/247.8
xg= 108.85g
Therefore, 108.9g of Silver can be produced from 125g of Ag2S
Answer:
The correct option is: Isoleucine
Explanation:
Peptides are the biological molecules containing amino acids which are linked together by peptide bonds. A polypeptide is a peptide chain in which more than 20 amino acids are linked together by peptide bond.
All polypeptide chains have a N-terminal and a C-terminal.
The N-terminal of a polypeptide is also known as the amino terminal. The N-terminal has a free amine group, which is generally on the left hand side of the polypeptide chain.
Therefore, the N-terminal or the amino terminal of the given polypeptide is Isoleucine (I).
