Answer:
The molecular formula of the compound is 
.
Explanation:
Let consider that given percentages are mass percentages, so that mass of each element are determined by multiplying molar massof the organic acid by respective proportion. That is:
Carbon
Hydrogen
Oxygen
Now, the number of moles (
), measured in moles, of each element are calculated by the following expression:
Where:
- Mass of the element, measured in grams.
- Molar mass of the element, measured in grams per mol.
Carbon (, 
)
Hydrogen (, 
)
Oxygen (, 
)
For each mole of organic acid, there are 7 moles of carbon, 6 moles of hydrogen and 2 moles of oxygen. Hence, the molecular formula of the compound is:
The heat of reaction : 50.6 kJ
<h3>Further explanation</h3>
Based on the principle of Hess's Law, the change in enthalpy of a reaction will be the same even though it is through several stages or ways
Reaction
N₂(g) + 2H₂(g) ⇒N₂H₄(l)
thermochemical data:
1. N₂H₄(l)+O₂(g)⇒N₂(g)+2H₂O(l) ΔH=-622.2 kJ
2. H₂(g)+1/2O₂(g)⇒H₂O(l) ΔH=-285.8 kJ
We arrange the position of the elements / compounds so that they correspond to the main reaction, and the enthalpy sign will also change
1. N₂(g)+H₂O(l) ⇒ N₂H₄(l)+O₂(g) ΔH=+622.2 kJ
2. H₂(g)+1/2O₂(g)⇒H₂O(l) ΔH=-285.8 kJ x 2 ⇒
2H₂(g)+O₂(g)⇒2H₂O(l) ΔH=-571.6 kJ
Add reaction 1 and reaction 2, and remove the same compound from different sides
1. N₂(g)+2H₂O(l) ⇒ N₂H₄(l)+O₂(g) ΔH=+622.2 kJ
2.2H₂(g)+O₂(g)⇒2H₂O(l) ΔH=-571.6 kJ
-------------------------------------------------------------------- +
N₂(g) + 2H₂(g) ⇒N₂H₄(l) ΔH=50.6 kJ
Given:
Volume of KOH = 53.0 mL
Concentration of KOH = 0.320 M
Volume of HNO3 = 28.0 mL
Concentration of HNO3 = 0.250 M
Balanced Equation:
KOH + HNO3 ===> KNO3 + H2O
0.320 0.250 0 0
H2O ===> H+ + OH-
Solve for the concentration of OH-
Answer:
SnCl₂·2 H₂O.
Explanation:
Relative atomic mass data from a modern periodic table:
- Sn: 118.710;
- Cl: 35.45;
- H: 1.008;
- O: 15.999.
How many moles of SnCl₂ formula units in this sample?
The first mass 4.90 grams contain both the SnCl₂ formula units and a number of water molecules. Luckily, the mass of the dehydrated salt 4.10 grams contains only SnCl₂.
Formula mass of tin (II) chloride SnCl₂:
.
Number of moles of tin (II) chloride SnCl₂ formula units in this sample:
.
How many moles of water molecules H₂O in this sample?
Water of crystallization exist as H₂O molecules in typical hydrated salts. The molar mass of these molecules will be:
.
The mass of water in the hydrated salt is the same as the mass that is lost when the water molecules are removed and the salt is dehydrated.
In other words,
.
.
What's the coefficient in front of water in the formula of this hydrated salt? In other words, how many water molecules are there in the compound for each SnCl₂ formula unit?
.
There are approximately two water molecules for each SnCl₂ formula unit. The formula of this compound shall thus be 
.
Answer:
Number of neutrons and stability
Explanation:
An isotope of an element is basically the same element but with different number of neutrons. For example here, boron can exist in the forms of boron-10 and boron-11, and so the latter would have one more neutron than the former one.
Adding an extra neutron may or may not disrupt the strong force that much, and so the half-life and stability of the new isotope can be slightly different than its most stable one.
