Ca + 2HCl = CaCl₂ + H₂
m(Ca)=60 g
c=1.25 mol/l
M(Ca)=40g/mol
v-?
m(Ca)/M(Ca)=m(HCl)/[2M(HCl)]=n(HCl)/2
n(HCl)=2m(Ca)/M(Ca)
n(HCl)=cv
cv=2m(Ca)/M(Ca)
v=2m(Ca)/{cM(Ca)}
v=2·60g/mol/{1.25mol/l·40g/mol}=2.4 l = 2400 ml
2400 milliliters of a 1.25 molar HCl solution would be needed
Answer:
The answer is "670.176 km".
Explanation:
Volume of the occupies of one M & M= 0.5 \ cm^3\\\\
M&M 1 mole
Calculating volume of M& M mole
Calculating the cube mole

Therefore 18 tractor trailers wouldn't be sufficient.
Answer:
24 atm.
Explanation:
From the question given above, the following data were obtained:
Initial volume (V₁) = 240 L
Initial pressure (P₁) = 2 atm
Final volume (V₂) = 20 L
Temperature = constant
Final pressure (P₂) =?
The final pressure required, can be obtained by using the Boyle's law equation as shown below:
P₁V₁ = P₂V₂
2 × 240 = P₂ × 20
480 = P₂ × 20
Divide both side by 20
P₂ = 480 / 20
P₂ = 24 atm
Thus, the final pressure required is 24 atm.
Answer: 2. cannot be an element.
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: methane 

Thus as it can be decomposed into its constituent elements, it is a compound.
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present.
Thus methane cannot be an element.