Acids are ionic compounds that break apart in water to form a hydrogen ion. The strength of an acid is based on the concentration of hydrogen ions in a solution. The more hydrogen ions, the stronger the acid. Bases are ionic compounds that break apart in water to form negatively charged hydroxide ions. The strength of the base is based on the concentration of hydroxide ions.
Hence, letter C is the correct answer.
Answer: The weight/weight % or percent by mass of the solute is 5.41 %.
Explanation:
Mass of the sodium sulfate,w = 9.74 g
Volume of the water = 165 mL
Density of the water = 1 g/mL

Mass of the water =
Mass of the solution, W:
Mass of solute + Mass of solvent =9.47 g + 165 g=174.47 g

The weight/weight % or percent by mass of the solute is 5.41 %.
First, you convert liters to moles.
Usually you have to go to grams but this is STP.
Get moles directly by dividing the 4 by STP (22.4)

About

or 0.18 moles whichever your teacher prefers
This equation C5H + O2 ---> CO2 + H2O has a mistake.
C5H is wrong. You missed the subscript of H.
I will do it for you assuming some subscript to show you the procedure, but you have to use the right equation to get the right balanced equation.
Assuming the tha combustion equation is C5H12 + O2 ---> CO2 + H2O
First you need to balance C, so you put a 5 before CO2 and get
C5H12 + O2 ---> 5CO2 + H2O
Now you count the hydrogens: 12 on the left and 2 on the right. So put a 6 before H2O and get:
C5H12 + O2 ---> 5CO2 + 6H2O
Now count the oxygens: 2 on the left and 16 on the right, so put an 8 on before O2:
=> C5H12 + 8O2 ---> 5CO2 + 6H2O.
You can verify that the equation is balanced
Answer:
The answer is endothermic as the heat flows into the system from the surroundings. The products are at higher energy than the reactants, as they have absorbed energy.