A. A pure chemical substance consisting of one type of atom
The temperature is constant which makes it the independent variable
Explanation:
The reaction between calcium hydroxide and nitric acid is as follows.
Number of reactant atoms are as follows.
Number of product atoms are as follows.
To balance the given chemical equation, multiply 
by 2 on reactant side and multiply 
by 2 on the product side.
Therefore, the balanced chemical equation will be as follows.
Answer:
MgCl2 > C4H9OH > CH4 > C3H8.
Explanation:
Alkanes do not form hydrogen bonds and are insoluble in polar solvents e.g water. The hydrogen bonds between water molecules are move away from an alkane molecule and this worsens as their Carbon chain / molecular weight increases.
MgCl2 is soluble in water. Water essentially breaks down the ionic crystal lattice and the resulting solution is slightly basic.
Alcohols are generally soluble in water and this is because of the -OH group and its ability to form hydrogen bonds with water molecules. As applied to alkanes, as the carbon chain in the alkyl group increases, the solubility decreases.
From the most soluble to the least soluble,
MgCl2 > C4H9OH > CH4 > C3H8.
