Answer:
ΔH° = -1815 kJ
Explanation:
The balanced chemical equation
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l)
tells us that 2220 kJ joules are released in the combustion of one mol propane,C3H8 . So what we need to solve this problem is to find how many moles of propane 20.0 L represent and do the calculation.
To do that, we will be using the Ideal Gas Law since we are told the volume, temperature, and pressure.
PV = nRT ∴ n = PV/RT
P: 1 atm
V: 20.0 L
R= 0.08206 Latm/kmol ( R constant for ideal gases)
T= 25 ºC + 273 = 298 k (Need to convert T to degree Kelvin)
Plugging the values
n = 1 atm x 20.0 L/ (0.08206 Latm/ k mol)
n = 0.82 mol
ΔH° =(-2220 kJ / 1 mol C3H8 ) 0.82 mol C3H8 = -1815 kJ
Answer:
b) 3x10³m³
Explanation:
The volume of each astronaut breathing in m³ is:
500cm³ * (1x10⁻⁶m³ / 1cm³) = 5x10⁻⁴m³
In 1 minute, the volume is:
5x10⁻⁴m³ * 15 = 7.5x10⁻³m³
In 1 hour:
7.5x10⁻³m³ /min * (60min / 1 hour) = 0.45m³/h
In 1 day:
0.45m³/h * (24h / 1 day) = 10.8m³/day
In 1 year:
10.8m³/day * (365 days / 1 year) = 3942m³ = 3.9x10³m³
That is approximately:
<h3>b) 3x10³m³</h3>
Answer:
26.25 mL
Explanation:
This is a dilution problem. First, let us calculate the volume of final solution needed:
The dog weighs 50 pounds and the sedative is administered at 0/7 ml per pound. Hence:
50 x 0.7 = 35 mL
A total volume of 35 mL, 2.5% solution of the sedative will be needed.
But 10% solution is available. There needs to be a dilution with saline water, but what volume of the 10% solution would be diluted?
initial volume = ?
final volume = 35 mL
initial concentration = 10%
final concentration = 2.5%
Using dilution equation:
initial concentration x initial volume = final concentration x final volume
initial volume =
= 2.5 x 35/10 = 8.75 mL
Hence, 8.75 mL of the 10% pre-mixed sedative will be required.
But 35 mL is needed? The 8.75 mL is marked up to 35 mL with saline water.
35 - 8.75 = 26.25 mL
<em>Therefore, 26.25 mL of saline water will be added to 8.75 mL of the 10% pre-mixed sedative to give 2.5%, 35 mL needed for the dog.</em>