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.
Answer:
Neon
Explanation:
Step 1: Given and required data
- Density of the gas (ρ): 1.57 g/L
- Ideal gas constant (R): 0.08206 atm.L/mol.K
Step 2: Convert T to Kelvin
We will use the following expression.
K = °C + 273.15 = 40.0 + 273.15 = 313.2 K
Step 3: Calculate the molar mass of the gas (M)
For an ideal gas, we will use the following expression.
ρ = P × M/R × T
M = ρ × R × T/P
M = 1.57 g/L × 0.08206 atm.L/mol.K × 313.2 K/2.00 atm
M = 20.17 g/mol
The gas with a molar mass of 20.17 g/mol is Neon.
The pressure of a gas is the force that the gas exerts on the walls of its container. When you blow air into a balloon, the balloon expands because the pressure of air molecules is greater on the inside of the balloon than the outside. Pressure is a property which determines the direction in which mass flows.
Answer:
C.
The air pressure creates a vacuum in the straw that pulls the air into the liquid.
Answer:
B
Explanation:
placenta comes after baby