D. ( Neither ultrasonic nor infrasonic vibrations can be heard by humans. )
Answer:
3grams
Explanation:
The reaction for the production of Magnesium dioxide will be
Mg + O2 → MgO
we have 5g of MgO (molar mass 40g)
no of moles of MgO = 5/40 = 0.125
Using unitary method we have
1 mole of Mg require 1 mole of MgO
0.125 Mole of MgO = 0.125mole of Mg
n = given mass /molar mass
0.125 = mass / molar mass
mass = 0.125* 24 = 3grams
Answer:
a. .125 mol b. 7.25g
Explanation:
a. To get the moles multiply the volume by the molarity.
.5L*.25M=.125mol NaCl
b. The molar mass is provided so multiply the moles by the molar mass to get the amount of grams of nacl.
.125mol*58molar mass=7.25g nacl to make the solution
Answer:
(a) 77.9 g/mol
(b) 3.18 g / L
Explanation:
<u>(a)</u> We need to use the ideal gas law, which states: PV = nRT, where P is the pressure, V is the volume, n is the moles, R is the gas constant, and T is the temperature in Kelvins.
Notice that we don't have moles; we instead have the mass. Remember, though that moles can be written as m/M, where m is the mass and M is the molar mass. So, we can replace n in the equation with m/M, or 21.3/M. The components we now have are:
- P: 0.880 atm
- V: 7.73 Litres
- n: m/M = 21.3 g / M
- R: 0.08206
- T: 30.00°C + 273 = 303 K
Plug these in:
PV = nRT
(0.880)(7.73) = (21.3/M)(0.08206)(303)
Solve for M:
M = 77.9 g/mol
<u>(b)</u> The equation for the molar mass is actually:
M = (dRT)/P, where d is the density
We have all the components except d, so plug them in:
77.9 = (d * 0.08206 * 298) / 1
Solve for d:
d = 3.18 g / L
Answer:
ΔH rx = -43.5 kJ / mol
Explanation:
In water, Xdissolves thus:
X(s) + H₂O(l) → X(aq) + H₂O(aq)
It is possible to find the heat in dissolution process using coffee cup calorimeter equation:
Q = -m×C×ΔT
<em>Where Q is heat, m is mass of solution (35.0g -density 1g/mL- + 2.20g = 37.2g), C is specific heat of solution (4.18J/g°C), and ΔT is change in temperature (26.0°C-15.0°C = 11.0°C)</em>
Replacing:
Q = -37.2g×4.18J/g°C×11.0°C
Q = -1710J = -<em>1.71kJ</em>
As enthalpy is the change in heat per mole of reaction, moles of X that reacted were:
2.20g X × (1mol / 56.0g) = <em>0.0393 moles</em>
As heat produced per 0.0393moles was -1.71kJ, heat per mole of X is:
-1.71kJ / 0.0393mol = -<em>43.5 kJ / mol = ΔH rx</em>
