Answer:- 448 mL of hydrogen gas are formed.
Solution:- It asks to calculate the volume of hydrogen gas formed in milliliters at STP when 0.020 moles of magnesium reacts with excess HCl acid. The balanced equation is:

There is 1:1 mol ratio between Mg and hydrogen gas. So, the moles of hydrogen gas is also equals to the moles of Mg reacted.
moles of Hydrogen gas formed = 0.020 mol
At STP, volume of 1 mol of the gas is 22.4 L. We need to calculate the volume of 0.02 moles of hydrogen gas.

= 0.448 L
They want answer in mL. So, let's convert L to mL using the conversion formula, 1L = 1000mL

= 448 mL
So, 0.020 moles of magnesium would produce 448 mL of hydrogen gas at STP on reacting with excess of HCl acid.
By the second law of thermodynamics:
Heat can not spontaneously flow from cold regions to hot regions without external work being performed on a system.
Heat transfer is the passage of thermal energy from a hot ( t B = 80° C ) to a colder body ( t A = 40° C ).
Answer: B ) Heat flows from object B to object A.
Answer:
motor oil
Explanation:
According to Oxford dictionary, viscosity refers to ''a quantity expressing the magnitude of internal friction in a fluid, as measured by the force per unit area resisting uniform flow.''
The higher the molecular weight of a substance, the greater its viscosity. This is because, the long chains in the viscous substance become entangled thereby increasing the internal friction in the liquid.
Motor oil is a heavier hydrocarbon than gasoline hence it is more viscous than gasoline.
Atomic mass W = 183.84 u.m.a
1 mole --------- 183.84
1.4 moles ---- ?
1.4 x 183.84 / 1 = 257.376 g
hope this helps!