Answer:
B) it is endothermic and the temperature decreased
Explanation:
Chemical reactions can be classified as endothermic and exothermic.
Endothermic reactions proceed with the absorption of heat energy (q) and have a positive value for q.
In contrast, Exothermic reactions proceed with the liberation of heat energy (q) and have a negative value for q.
It is given that the value of q = +450 J. Since q is positive, this implies that heat energy is absorbed from the surroundings resulting in a fall in temperature. Hence the reaction is endothermic.
The STP is Standard temperature and pressure.
Standard temperature is defined as zero degrees Celsius (0° C)
Standard pressure supports 760 millimeters in a mercurial barometer (760 mmHg)
we have that
760 mmHg= 1 atm
therefore
the answer is 0 deg C and 1 atm.
Answer:
Speed
Explanation:
Aliyah must have been trying to find her speed.
The speed is a measure of how fast an object or a body is and it is calculated by finding the ratio of distance with time. Mathematically,
speed = 
with a unit of m/s.
<em>Hence, with the distance measured on the ground and Aliyah trying to find the time it will take her to cover the distance while running, she must have been trying to find how fast she can run, that is, speed. </em>
Answer:
n = 4678.13 mol
Explanation:
Given data:
Temperature = 21°C
Pressure = 746 mmHg
Volume = 115 m³
Number of moles = ?
Solution:
21+273 = 294 k
746 /760 = 0.982 atm
115×1000 = 115000 L
PV = nRT
n = PV/RT
n = 0.982 atm × 115000 L /0.0821 atm. L. K⁻¹. mol ⁻¹× 294 k
n = 112930 atm. L/24.14 atm. L. mol ⁻¹
n = 4678.13 mol
Freeze drying<span> (or lyophilization) removes water from the ice cream by lowering the </span>air pressure<span> to a point where ice sublimates from a </span>solid<span> to a </span>gas<span>. The ice cream is placed in a </span>vacuum chamber<span> and frozen until the water </span>crystallizes<span>. The air pressure is lowered, creating a partial vacuum, forcing air out of the chamber; next heat is applied, </span>sublimating<span> the ice; finally a freezing coil traps the vaporized water. This process continues for hours, resulting in a freeze-dried ice cream slice. </span>
