What are the physical and chemical properties and changes of soap?
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Answer:
B) 12.9 grams.
Explanation:
How many moles of molecules in that 6.30 L of H₂?
The volume of one mole of an ideal gas at STP (0 °C, 1 atm) is 22.4 liters.
(The volume of that one mole of gas at STP will be 22.7 liters if STP is defined as 0 °C and 10⁵ Pa).
.
How many moles of Na will be needed?
The coefficient in front of Na in the equation is twice the coefficient in front of H₂. It takes two moles of Na to produce one mole of H₂.
.
What's the mass of that many Na atoms?
Refer to a modern periodic table. The molar mass of ₁₁Na is 22.990. The mass of one mole of Na atoms is 22.990 gram. The mass of 0.5625 moles of Na atoms will be
.
(2 sig. fig. as in the volume of the H₂ gas.)
Answer:
Percent yield = 92.5%
Explanation:
The question asks for the percent yield which can be defined as:
Where the actual yield is <em>how much product was obtained</em>, in this case 6.11 g of Ca(OH)₂, and the theoretical yield is <em>how much product could be obtained with the given reactants theoretically</em>, that is if the reaction would work perfectly. So we need to calculate first the theoretical yield.
1. First lets write the chemical equation reaction correctly and check that it is balanced:
CaO + H₂O → Ca(OH)₂
2. Calculate the amount of product Ca(OH)₂ that can be obtained with the given reactants (theoretical yield), which are 5.00g of CaO and excess of water. So the amount of CaO will determined how much Ca(OH)₂ we can obtained.
For this we'll use the molar ratio between CaO and Ca(OH)₂ which we see it is 1:1. For every mol of CaO we'll obtain a mol of Ca(OH)₂. So lets convert the 5.00 g of CaO to moles:
Molar Mass of CaO: 40.078 + 15.999 = 56.077 g/mol
moles of CaO = 5.00 g / 56.077 g/mol = 0.08916 moles
As we said before from the molar ratio moles of Ca(OH)₂ = moles of CaO
So the moles of Ca(OH)₂ that can be obtained are 56.077 g/mol
We need to convert this value to grams:
Molar Mass of Ca(OH)₂ = 40.078 + (15.999 + 1.008)*2 = 74.092 g/mol
Theoretical yield of Ca(OH)₂ = 0.08916 moles x 74.092 g/mol = 6.606 g
3. Calculate the percent yield:
Percent yield = (6.11 g / 6.606g) x 100 = 92.5 %