Answer:
Kindly, see the attached image.
Explanation:
As clear in the attached image:
- It represents the cooling curve of water.
- It starts from 20°C, the water exists in the liquid phase.
- With time the temperature is decreased, reaching 0°C, the two phases (liquid and solid) are co-exist.
- Then, with further cooling and under 0°C reaching -20°C, all the water are exist in the solid phase (Ice).
<em>Kindly, see the attached image that clarify the cooling graph of water as it passes from 20°C to –20°C. </em>
<em />
Answer: A and D
Explanation: isotopes must have same atomic number but different mass number due to the difference in their Neutron number
Explanation:
Mg(s) + Cr(C2H3O2)3 (aq)
Overall, balanced molecular equation
Mg(s) + Cr(C2H3O2)3(aq) --> Mg(C2H3O2)3(aq) + Cr(s)
To identify if an element has been reduced or oxidized, the oxidation number is observed in both the reactant and product phase.
An increase in oxidation number denotes that the element has been oxidized.
A decrease in oxidation number denotes that the element has been reduced.
Oxidation number of Mg:
Reactant - 0
Product - +3
Oxidation number of Cr:
Reactant - +3
Product - 0
Note: C2H3O2 is actually acetate ion; CH3COO- The oxidatioon number of C, H and O do not change.
Oxidized : Mg
Reduced : Cr
Answer:
(a) Condensation:Exothermic
(b) Sublimation: Endothermic
(c) Vaporization: Endothermic
(d) Freezing: Exothermic
Explanation:
When a phase change occurs, for example going from a liquid to a gas we need to increase the kinetic energy of the molecules to escape to the gas phase where the kinetic energy of the molecules is greater. By the contrary if we remove energy we slow down the molecules increasing their atttraction and slowing them as it occurs when the goes into the liquid state, hence this phase change is exothermic.
(a) Condensation : when the phase change is from a gas by definition we have a condensation phase chanhe. The reaction is exothermic, we need to cool the gas to condense.
(b) Sublimation: crystals of iodine disappear from an evaporating dish as they stand in a fume hood : this phase change receives the name of sublimation and it occurs when a solid goes directly to the gas phase without going through the liquid phase. We need to increase the energy of the molecules so it can go to the gas phase and the change is endothermic.
(c) Vaporization : rubbing alcohol in an open container slowly disappears: this phase change is vaporization and by difinition is when the liquid goes to the gas phase, hence its name vaporization. The change is endothermic, we need heat from the sorroundings to give the molecules of the liquid enough energy to escape into the vapor phase.
(d) Molten lava from a volcano turns into solid rock : this phase change is freezing and we need to lower the energy of the liquid by releasing it to the sorroundings, therore it is an exothermic phase change.
Answer:
It has 4 valence electrons
Explanation:
Tin atoms have 50 electrons and 50 protons with 4 valence electrons in the outer shell.
