Explanation:
The basis for classifying changes in matter into physical and chemical change is to see if a material is altered after going through a process.
In a physical change only the state of matter is usually altered especially its form or shape.
Chemical change alters a substance by producing new kinds that are totally different from it.
- In a chemical change, new kinds of matter are usually formed.
- Such changes are usually irreversible.
- Change of state is a reversible process.
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The mass of substance which consists the equal number of particles as 12 grams of Carbon-12 is said to be mole.
For example:
The balanced chemical equation for production of water from hydrogen and oxygen is:
![2H_2(g) + O_2(g) \rightarrow 2H_2O(l)](https://tex.z-dn.net/?f=2H_2%28g%29%20%2B%20O_2%28g%29%20%5Crightarrow%202H_2O%28l%29)
That means 2 moles of
reacts with 1 mole of
to give 2 moles of
.
The given formula is
.
Hence, 4 represents the number of moles in
formula that is 4 moles of
.
The number of atoms of sodium,
in
is:
![4 \times 2 = 8](https://tex.z-dn.net/?f=4%20%5Ctimes%202%20%3D%208)
The number of atoms of sulfur,
in
is:
![4 \times 1 = 4](https://tex.z-dn.net/?f=4%20%5Ctimes%201%20%3D%204)
The number of atoms of oxygen in,
in
is:
![4 \times 3 = 12](https://tex.z-dn.net/?f=4%20%5Ctimes%203%20%3D%2012)
Al
Na
S
O
Br
Ca
Explanation:
The atomic radius is taken as the half of the inter-nuclear distance between two covalently bonded atoms of non-metallic elements. It is also the half - distance between two nuclei in the solid state of metals.
Across a period on the periodic table, atomic radii decreases due to increase in the nuclear charge without an attendant increase in the number of electronic shells.
Down a group atomic radii increases due to successive shells of electrons being added.
a. Al or B : down a group III, so aluminium is larger
b. Na or AI
: across a period so Na is larger
c. S or o
: down group VI so sulfur is larger
d. O or F
: across a period so oxygen is larger
e. Br or CI
: down a group VII so Br is larger
f. Mg or Ca: down a group II so Ca is larger
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Answer:
Oxidation is the loss of electrons, that is, addition of electronegetive elements, example is addition of oxygen. Also, removal of electropositive elements, example is removal of hydrogen.
Explanation: a) In the presence of excess oxygen, propane burns in air, which gives the following chemical equation:
C3H8 + 5O2⇒ 3CO2 + 4H2O +Heat
b) When insufficient oxygen or too much oxygen is present for complete combustion, the following equation is given:
2C3H8 + 9O2 ⇒ 4CO2 + 2CO + 8H2O + Heat
c) At the anode( negative terminal): O∧2- ⇒ O + e
Oxygen accepts electron.
d) At cathode ( positive terminal): H∧+ + e∧- ⇒ H
Hydrogen donates electron
d) Nernst equation for reversal potential is given as follows:
E= RT/zF In{ion outside cell}/{ion inside cell}= 2.303 RT/zF In{ion outside cell}/{ion inside cell}
Answer:
Reactions, 2, 3 and 5 make precipitates
Explanation:
1. The halogens always make aqueous salts with elements from group 1
2. Phosphate anion can make insoluble salts, the same as carbonate.
3. Nitrate anion always make aqueous salts
4. Sulfate anion makes aqueous salts except with Ag⁺, Pb⁺² and group 2
1. KI(aq) + NaCl(aq) → KCl(aq) + NaI(aq)
2. 2Na₃PO₄ (aq) + 3CoCl₂(aq) → 6NaCl(aq) + Co₃(PO₄)₂(s) ↓
3. Na₂CO₃ (aq) + CuCl₂ (aq) → 2NaCl (aq) + CuCO₃ (s) ↓
4. 2LiNO₃ (aq) + Na₂SO₄ (aq) → Li₂SO₄ (aq) + 2NaNO₃(aq)
5. CrCl₂ (aq) + Li₂CO₃ (aq) → 2LiCl (aq) + Cr₂(CO₃)₂ (s) ↓