Answer:
The formula of Al³⁺ and SO₄²⁻ is aluminum sulfate.
Explanation:
The formula for aluminum sulfate is Al₂(SO₄)₃. If we say in terms of ions. The ions are Al³⁺. It is a positive ion or the cation. Other ion is SO₄²⁻. It is sulfate ion. It is anion.
Aluminum sulphate is used in water purification and as a mordant in dyeing and printing textiles.
Hence, the formula of Al³⁺ and SO₄²⁻ is aluminum sulfate.
 
        
             
        
        
        
If heat energy is transferred from direct contact between a warm object and a cold object, it has been transferred by Convection.
Heat is transferred through convection, which is the large-scale movement of molecules inside gases and liquids. Conduction is used to move heat from the object to the fluid initially, but fluid motion is responsible for the bulk of the heat transfer.
The transfer of heat between two bodies by currents of moving gas or fluid is known as convection on heat transfer. In free convection, air or water rises and is replaced by a cooler parcel of air or water as it moves away from the hot body.
To learn more about convection please visit - 
brainly.com/question/16635311
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Well the multiple choices for this question would be helpful, but from my own knowledge I would say: 
Magnetic fields have north and south magnetic poles.
Magnetic fields have various characteristics which includes; they originate from the north poles and flow towards the south poles, they are exhibited in the form of magnetic field lines. Magnetic fields lines never cross one another,they all have the same strength and seek the path of least resistance between opposite magnetic poles etc.
 
        
             
        
        
        
Answer: 400K
Explanation:
Given that,
Original volume of balloon V1 = 3.0L
Original temperature of balloonT1 = 27°C
Convert the temperature in Celsius to Kelvin 
(27°C + 273 = 300K)
New volume of balloon V2 = 4.0L
New temperature of balloon T2 = ?
Since volume and temperature are given while pressure is constant, apply the formula for Charle's law
V1/T1 = V2/T2
3.0L/300K = 4.0L/T2
To get the value of T2, cross multiply 
3.0L x T2 = 4.0L x 300K
3.0LT2 = 1200LK
Divide both sides by 3.0L
3.0LT2/3.0L = 1200LK/3.0L
T2 = 400K
Thus, at a temperature of 400 Kelvin, the balloon would have a volume of 4.0L.