The scientist that invented a model that shows the electron cloud is Neil Bohr. <span />
Answer:
136 g Al₂O₃
Explanation:
Assuming you do not need to find the limiting reactant, to find the mass of Al₂O₃, you need to (1) convert grams O₂ to moles O₂ (via molar mass), then (2) convert moles O₂ to moles Al₂O₃ (via mole-to-mole ratio from equation coefficients), and then (3) convert moles Al₂O₃ to grams Al₂O₃ (via molar mass). It is important to arrange the conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value (64.0 g).
Molar Mass (O₂): 32 g/mol
Molar Mass (Al₂O₃): 102 g/mol
4 Al + 3 O₂ -----> 2 Al₂O₃
64.0 g O₂ 1 mole 2 moles Al₂O₃ 102 g
----------------- x -------------- x ------------------------ x ------------- = 136 g Al₂O₃
32 g 3 moles O₂ 1 mole
Answer:
Na₂CO₃ · 10H₂O
Explanation:
The formula for sodium carbonate hydrate is:
Na₂CO₃ · xH₂O
The unknown "x" is the number of water molecules contained in the hydrate.
To find "x" we have to use the hydrogen percentage in the sample, 7.05 % H.
First we calculate the molecular weight of Na₂CO₃ · xH₂O:
molecular weight of Na₂CO₃ · xH₂O = 23 × 2 + 12 + 16 × 3 + 18x
molecular weight of Na₂CO₃ · xH₂O = 106 + 18x g/mole
Now we devise the fallowing reasoning tanking in account 1 mole of Na₂CO₃ · xH₂O:
if in 106 + 18x grams of Na₂CO₃ · xH₂O we have 2x grams of hydrogen
then in 100 grams of Na₂CO₃ · xH₂O we have 7.05 grams of hydrogen
106 + 18x = (100 × 2x) / 7.05
106 + 18x = 28.4x
106 = 28.4x - 18x
106 = 10.4x
x = 106 / 10.4
x = 10.2 ≈ 10
The formula for the washing soda is Na₂CO₃ · 10H₂O.
1. P = F/A; weight is a force (the force of gravity on an object), so divide the weight by the area given. P = 768 pounds/75.0 in² = 10.2 pounds/in².
2. Using the same equation from question 1, rearrange it to solve for A: A = F/P. We're given the force (the weight) and the pressure, so A = 125 pounds/3.25 pounds/in² = 38.5 in².
3. Again, using the same equation from question 1, rearrange it this time to solve for F: F = PA = (4.33 pounds/in²)(35.6 in²) = 154 pounds.
4. We can set up a proportion given that 14.7 PSI = 101 KPa. This ratio should hold for 23.6 PSI. In other words, 14.7/101 = 23.6/x; to solve for x, which would be your answer, we compute 23.6 PSI × 101 kPa ÷ 14.7 PSI = 162 kPa.
5. We are told that 1.00 atm = 760. mmHg, and we want to know how many atm are equal to 854 mmHg. As we did with question 4, we set up a proportion: 1/760. = x/854, and solve for x. 854 mmHg × 1.00 atm ÷ 760. mmHg = 1.12 atm.
6. The total pressure of the three gases in this container is just the sum of the partial pressures of each individual gas. Since our answer must be given in PSI, we should convert all our partial pressures that are not given in PSI into PSI for the sake of convenience. Fortunately, we only need to do that for one of the gases: oxygen, whose partial pressure is given as 324 mmHg. Given that 14.7 PSI = 760. mmHg, we can set up a proportion to find the partial pressure of oxygen gas in PSI: 14.7/760. = x/324; solving for x gives us 6.27 PSI oxygen. Now, we add up the partial pressures of all the gases: 11.2 PSI nitrogen + 6.27 PSI oxygen + 4.27 PSI carbon dioxide = 21.7 PSI, which is our total pressure.
