I got B. Because the answer is K2SO4, I got it right on my test so I know its right
Answer: The correct answer is option B.
Explanation: Reactivity of elements is defined as the tendency to loose or gain electrons.
These reactions are a type of single displacement reactions. A single displacement reaction is a type of reaction in which an element displaces another element in a chemical reaction. These are studied with the help of reactivity series.
The element which lies above in the reactivity series can easily displace the element which lies below in the reactivity series.
Option A: This reaction will not yield a stable product because Zinc lies below Aluminium in the reactivity series.

Option B: This reaction will yield a stable product because Sodium lies above Calcium in the reactivity series.

Option C: This reaction will not yield a stable product because Hydrogen lies below Magnesium in the reactivity series.

Option D: This reaction will not yield a stable product because Calcium lies below Barium in the reactivity series.

Option E: This reaction will not yield a stable product because barium lies below Lithium in the reactivity series.

Answer: 4.96 moles
Explanation:
C5H12 is the chemical formula for pentane, the fifth member of the alkane family.
Given that,
number of moles of C5H12 = ?
Mass in grams = 357.4 g
Molar mass of C5H12 = ?
To get the molar mass of C5H12, use the atomic mass of carbon = 12g; and Hydrogen = 1g
i.e C5H12 = (12 x 5) + (1 x 12)
= 60g + 12g
= 72g/mol
Now, apply the formula
Number of moles = Mass / molar mass
Number of moles = 357.4g / 72g/mol
= 4.96 moles
Thus, 4.96 moles of C5H12 that are contained in 357.4 g of the compound.
Molar mass NaOH = 40.0 g/mol
Volume in liters of solution :
5 mL / 1000 => 0.005 L
number of moles :
4 / 40 => 0.1 moles
M = n / V
M = 0.1 / 0.005
= 20 mol/L or 20 M
hope this helps!