<h3>
Answer:</h3>
915 Joules
<h3>
Explanation:</h3>
- The heat of fusion is the heat that is required to convert a given mass of a substance from solid state to liquid state without change in temperature.
- In this case, we are given specific heat of a substance as 122 joules per gram
- It means that amount of heat equivalent to 122 joules is required to change 1 gram of the substance from solid state to liquid state.
- Therefore, we can determine the amount of heat needed to change 7.5 grams of the substance from solid to liquid state.
1 g = 122 Joules
7.5 g = ?
= 122 × 7.5
= 915 Joules
Thus, 7.5 g of the substance at its melting point will require 915 Joules of heat to melt.
Answer:
An alcohol thermometer can measure the freezing point of a liquid that freezes at −80 °C.
Explanation:
A thermometer is a device used to measure temperature. A thermometer must contain a thermometric substance. A thermometric substance is any substance having a particular physical property that changes with temperature.
For all liquid-in-glass thermometers, the property that changes with change in temperature is the height of the liquid. There are two kinds of liquid-in-glass thermometers; mercury-in-glass thermometer and alcohol-in-glass thermometer.
Alcohol-in-glass thermometer measures very low temperatures up to as low as -115°C. If it measures such a low temperature, then it can efficiently measure -80°C hence the answer.
Alcohol-in-glass thermometers have a narrower temperature range than mercury-in-glass thermometer. The later is well adapter for the measurement bof higher tempetures up to 357°C.
Answer:
B and C
Explanation:
When we have to do a buffer solution we always have to choose the reaction that has the <u>pKa closer to the desired pH value</u>. When we find the pKa values we will obtain:
![pKa_1=-Log[6.9x10^-^3]=2.16](https://tex.z-dn.net/?f=pKa_1%3D-Log%5B6.9x10%5E-%5E3%5D%3D2.16)
![pKa_2=-Log[6.2x10^-^8]=7.20](https://tex.z-dn.net/?f=pKa_2%3D-Log%5B6.2x10%5E-%5E8%5D%3D7.20)
![pKa_3=-Log[4.8x10^-^13]=12.31](https://tex.z-dn.net/?f=pKa_3%3D-Log%5B4.8x10%5E-%5E13%5D%3D12.31)
The closer value is pKa2 with a value of 7.2. Therefore we have to use the second reaction. In which 
is the <u>acid</u> and 
is the <u>base</u>. Therefore the answer for the first question is B and the answer for the second question is C.
Answer:
Collisions between gas particles are elastic; there is no net gain or loss of kinetic energy.
Explanation:
When a gas is paced in a container, the molecules of the gas have little or no intermolecular interaction between them. There is a lot of space between the molecules of the gas.
The gas molecules move at very high speed and collide with each other and with the walls of container.
The collision of these particles with each other is perfectly elastic hence the kinetic energy of the colliding gas particles do not change.
