A student received a helium birthday balloon from a friend. Attached to it was the scanner card indicating that it had been filled with 1.2L of helium gas. Curious, as to how much helium this really was, she calculated the number of helium atoms contained in the balloon, assuming standard temperature and pressure. She discovered that the balloon contained _______atoms of helium.
A. 7.23 × 1023
Incorrect. Check your calculations.
B. 5.02 × 1023
Incorrect. Check your calculations.
C. 3.23 × 1022
Correct! You got it right.
D. 3.1 × 10-23
Incorrect. Check your calculations.
To determine why CO2 gas sinks in air, students were asked to compare the mass of a single molecule of carbon dioxide to a single molecule of N2, since 78% of air is nitrogen gas. They found the mass of 1 CO2 molecule to be —
A. 1.37 × 10-2
Incorrect. Check your calculations.
B. 2.69 × 10-22
Incorrect. Check your calculations.
C. 3.72 × 10-23
Incorrect. Check your calculations.
D. 73.1 × 10-23
Correct! You got it right.
A medical supply company wants to make available a new 3L cylinder for its patients that require portable oxygen. The machine that fills the cylinders is calibrated by mass. Since one mole of any gas is 22.4L at STP, how many grams of O2 can be put in a 3.0L cylinder at STP?
A. 4.29 g
Correct! You got it right.
B. 7.46 g
Incorrect. Check your calculations.
C. 8.06 g
Incorrect. Check your calculations.
D. 238.9 g
Incorrect. Check your calculations.
A student was impressed by a Chem -Team demonstration done by a local university group. Seeking to replicate one of the demonstrations as part of a presentation he was to make for his class, he needed to be sure that the volume of hydrogen gas was going to be less than 50mL to avoid an unsafe explosion from the following reaction: Mg + 2HCl (1.0M) → MgCl2 + H2. How much Mg should he use?
A. 0.027g Mg
Incorrect. Check your calculations.
B. 0.054g Mg
Correct! You got it right.
C. 0.54g Mg
Incorrect. Check your calculations.
D. 0.61g Mg
Incorrect. Check your calculations.