Answer:
- <em>Hydration number:</em> 4
Explanation:
<u>1) Mass of water in the hydrated compound</u>
Mass of water = Mass of the hydrated sample - mass of the dehydrated compound
Mass of water = 30.7 g - 22.9 g = 7.8 g
<u>2) Number of moles of water</u>
- Number of moles = mass in grams / molar mass
- molar mass of H₂O = 2×1.008 g/mol + 15.999 g*mol = 18.015 g/mol
- Number of moles of H₂O = 7.9 g / 18.015 g/mol = 0.439 mol
<u>3) Number of moles of Strontium nitrate dehydrated, Sr (NO₃)₂</u>
- The mass of strontium nitrate dehydrated is the constant mass obtained after heating = 22.9 g
- Molar mass of Sr (NO₃)₂ : 211.63 g/mol (you can obtain it from a internet or calculate using the atomic masses of each element from a periodic table).
- Number of moles of Sr (NO₃)₂ = 22.9 g / 211.63 g/mol = 0.108 mol
<u>4) Ratio</u>
- 0.439 mol H₂O / 0.108 mol Sr(NO₃)₂ ≈ 4 mol H₂O : 1 mol Sr (NO₃)₂
Which means that the hydration number is 4.
2. The coefficients represent to molar ratios in a balanced equation.
The answer to this question would be: Because the increase of temperature will increase volume.
Using PV=nRT formula we can see that temperature increase will cause an increase in volume. Overheating will cause the volume increase, then increasing the volume. If the percent value used is based on the volume, it will seem that the water is increased. But if the percent is using mass, there will be no increases.
That is why sometimes scientists using molality in a reaction with high temperature changes.
If I made no mistake in calculation, the given answer must be correct...(tried my best)
elements : carbon hydrogen oxygen Fluorine
composition [C] 24 3 16 57
M r 12 1 16 19
(divide C by Mr) 2 3 1 3
(Divide by smallest value) 2 3 1 3
(smallest value = 1...so all value remained constant)
Empirical formula : C2H3OF3
if molar mas = 100 g per mole, then
first step calculate Mr. of empirical formula: [= 100]
Them molecular formula = empirical formula
