540g
Explanation:
Given parameters:
Mass of the aluminium oxide = 1020g
Unknown:
Mass of aluminium = ?
Solution:
To find the mass of the aluminium formed from this reaction, we work from the known to the unknown. The known here is the mass of the aluminium oxide.
Using this mass, find the number of moles in the aluminium and relate it using the balanced equation to that of the unknown aluminium.
From the number of moles, we can easily find the mass of the aluminium.
Solving:
Balanced equation:
2Al₂O₃ → 4Al + 3O₂
Number of moles of Al₂O₃ = 
Molar mass of Al₂O₃ = 2(27) + 3(16) = 102g/mol
Number of moles = 
= 10mol
From the balanced equation:
2 moles of Al₂O₃ produced 4 moles of Al
10 moles of Al will produce 
= 20moles of Al
Mass of Al = number of moles of Al x molar mass of Al = 20 x 27 = 540g
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Answer:
d). A catalyst lowers the activation energy for a chemical reaction.
Explanation:
From the given choices, it is true that a catalyst lowers the activation energy for a chemical reaction.
The activation energy is the energy barrier that must be overcome before a chemical reaction can occur.
Some reactions have very high activation energy and would not occur without the introduction of a catalyst.
The catalyst brings the reactants into contact by removing the energy deficiency in the system.
Answer is number 4.
The above diagram shows a part of our solar system.The planet which is very close to the sun is Mercury. Hence, No.1 is Mercury and 2 and 3 are Venus and Earth respectively. Moon is an astronomical body which orbit planet Earth. Hence moon should be shown near to the planet Earth.
The structures shown are examples of Constitutional Isomer.
In Chemistry, an isomer refers to a molecule that is similar to another but has differences. These differences can be:
- A difference in the constitution: The molecules have the same formula but the connectivities between elements or arrangement is different.
- Arrangement in space: The molecules have the same formula and connectivity, but they look different to do an arrangement in space of a position.
The molecules shown have the same formula because the elements in each pair are the same. However, the way these elements are connected is slightly different because the Br and the CH3 are connected to different carbons.
Based on this, the difference is the connectivity or constitution, and therefore these are constitutional isomers.
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Answer:
Ka2 values should be used in obtaining pKa2 in the Henderson–Hasselbalch equation
Explanation:
During first dissociation from H3PO4 to H2PO4-, ka1 will be used, and from H2PO4-to HPO4-, ka2 values will be used, hence a buffer solution containing H2PO4-and HPO4-will use ka2 in obtaining pKa2 in the Henderson–Hasselbalch equation.
