<span>We can use rocks to determine if the animals from to day have changed from the past.
Rocks also help us know if rivers once flowed through an area.
We use them to find out what type of animals live then that are extinct now.</span>
Answer:
A. endothermic.
A. Yes, absorbed.
Explanation:
Let's consider the following thermochemical equation.
2 HgO(s) ⇒ 2 Hg(l) + O₂(g) ΔH = 182 kJ
The enthalpy of the reaction is positive (ΔH > 0), which means that the reaction is endothermic.
182 kJ are absorbed when 2 moles of HgO react (molar mass 216.59 g/mol). The heat absorbed when 72.8 g of HgO react is:
The physical method that can be used for obtaining a sample of salt from a small beaker of salt and water would be evaporation.
<h3>Separation of salt and water</h3>
A mixture of salt and water can be separated by a method known as evaporation. This is based on the assumption that the salt in question is a water-soluble salt.
In order to separate the salt/water mixture:
- Place the mixture in a suitable evaporating dish
- Boil the mixture until all the water evaporates.
- The remaining residue would be the salt
Care should be taken not to overheat the residue in order to avoid melting. Evaporation is generally used to separate a mixture of water and soluble salt. If the salt is insoluble, filtration using a suitable filter paper will filter off the salt while the water is collected as the filtrate.
More on evaporation can be found here: brainly.com/question/1097783
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Which physical method can be used for obtaining a sample of salt from a small beaker of salt water?
Explanation:
atomic hydrogen torch utilizes an electric arc whereby two closely - but not touching electrodes - result in the release of powerful electric spark as the current tries to flow through the gap. The gap is filled with hydrogen gas in an atomic hydrogen torch rather than air. The electric arch is split the hydrogen gas molecules into hydrogen atoms (some in plasma form). When the hydrogen atoms land on cooler objects like the metal being welded or cut, they region back to H₂ molecules releasing enormous amounts of heat on the surface. Surface temperatures can reach 4000 °C. The use of hydrogen gas protects the metal being welded from oxidation. Oxidation may compromise the quality of the weld.
Learn More:
For more on other welding torches check out;
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