Answer:
Because it can cause health problems or injuries to our sense organs.
Explanation:
Chemicals in the laboratory are made up of different constituents, which may be dangerous or injurious to health. This is the reason why safety measures or precautions have to be taken when working in the laboratory. One of those safety measures is that "one should never use taste, touch, or smell to identify an unknown chemical".
This is so because a chemical that is unknown amounts to the fact that what such chemical contains is unknown, hence, the chemical might have the ability to cause harm or injuries to the sense organ. For example, a conc. acid that is tasted will burn the tongue etc.
Answer:
B. a change in their state or substance
Explanation:
A change of state consists of a physical process in which the structure of the substance changes, its appearance. EXAMPLE: in the merger, the solid state becomes liquid, changes the rearrangement of particles from being highly compacted to being less compact.
Answer:
Explanation:
It is easier if you convert the kelvin temperature into Celsius degrees:
- ºC = T - 273.15 = 150 - 273.15 = -123.15ºC
Now, you know that that is a very cold temperature. Thus, may be the oxygen is not gas any more but it changed to liquid . . . or solid?
You must search for the boiling point and melting (freezing) point of oxygen in tables or the internet. At standard pressure (about 1 atm) they are:
- Melting point: −218.79 °C,
- Boiling point: −182.962 °C
That means that:
- below -218.79ºC oxygen is solid (not our case).
- between -218.79ºC and -182.962ºC oxygen is liquid (not our case)
- over -182.962ºC oxygen is a gas. This is our case, because -123.15ºC is a higher temperature than -182.962ºC.
Hence, <em>the state of matter of oxygen at 150K</em>, and standard pressure, is gas.
Answer:
-241 kJ/mol
Explanation:
Let's consider the reaction of hydrogen with excess oxygen to form water.
2 H₂ + O₂ ⟶ 2 H₂O
When 2.16g of hydrogen reacts with excess oxygen, 258 kJ of heat are released, that is, Q = -258 kJ. Considering that the molar mass of hydrogen is 2.02 g/mol, the change of enthalpy associated with the reaction of 1.00 mol of hydrogen gas is:
ΔH° = -258 kJ/2.16 g × (2.02 g/1.00 mol) = -241 kJ/mol
Explanation:
To form bonds with noble gases, a lot of energy is required to form those bonds. Halogens, on the other hand, are extremely reactive. ... The halogens tend to be very reactive, while the noble gases are in no way reactive and don't bond easily, if at all.
