Answer:
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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.
Answer:
55.75g
Explanation:
From
m/M = CV
Where
m= required mass of solute
M= molar mass of solute
C= concentration of solution
V= volume of solution=675ml
Molar mass of solute= 3(23) + 31 + 4(16)= 69+31+64=164gmol-1
Number of moles of sodium ions present= 1.5× 675/1000= 1.01 moles
Since 1 mole of Na3PO4 contains 3 moles of Na+
It implies that 1.01/3 moles of Na3PO4 are present in solution= 0.34moles
mass of Na3PO4= number of moles × molar mass= 0.34 × 164 =55.75g
The correct answer is 30 seconds
