What chemical change occurred in the following reaction? Mg2+(aq)+2OH−(aq)⟶ Mg(OH)2(s)
2 answers:
Answer : When magnesium salts combine with the alkaline water it induces precipitation of solid .
Explanation :
- Chemical change : The chemical change occurs when a substance combine with the another substance to form a new substance.
It can not be easily reversible.
The new product is formed or precipitate may be formed.
- Physical change : The physical change occurs when a substance combine with the another substance then no new compound is formed.
It can be reversible.
No new product is formed only changes occurs in the state or phase.
As per question, when magnesium salts combine with the alkaline water it induces precipitation of solid .
The balanced chemical reaction is,
That mean a new compound is formed by this reaction. So, the chemical change occurred in this reaction.
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Answer:
The correct answers are:
- Krypton: density= 2.8 g/L
- Molar Mass= 63.99 g/mol
- Mass of O₂= 15.29 g
Explanation:
The general equation of an ideal gas is the folllowing:
P x V = n x R x T
Where: P= pressure (in atm), V= volume; n= number of moles, R= gas constant (0,082 L.atm/K.mol) and T= temperature (in K).
<u>For krypton</u>:
P= 671 mmHg = 0,882 atm
V= 478 ml x 1000 ml/1 L= 0,478 L
T= 47ºC= 320 K
MM= 83.8 g/mol (from Periodic Table, Kr is an inert gas so it is a monoatomic gas)
P x V = n x R x T
Since the number of moles of a compound can be calculated by dividing the mass of compound (m) into its molar mass (MM):
n= m/MM
We can replace the expression in the first equation to obtain:
m/V=
Density (d) is equal to the mass per volume (m/V), so we can directly calculate the density:
d= m/V= \frac{P x MM}{R x T}=
= (0.882 atm x 83.8 g/mol)/(0.082 L.atm/K.mol x 320 K)
= 2.81 g/L
<u>For the gas:</u>
d= 2.18 g/L
T= 66ºC= 339 K
P= 720 mmHg= 0.947 atm
d= \frac{P x MM}{R x T}
⇒MM =
= (2.18 g/L x 0.082 L.atm/K.mol x 339 K)/(0.947 atm)
= 63.99 g/mol ≅ 64 g/mol
<u>For the O₂</u>:
V= 5.60 L
P= 1.75 atm
T= 250 K
MM(O₂) = 2 x Atomic Mass O= 2 x 16 g/mol= 32 g/mol
We can use the second equation:
P x V= \frac{m}{MM} x R x T
⇒ m = = (1.75 atm x 5.6 L x 32 g/mol)/(0.082 L.atm/K.mol x 250 K)
= 15.29 g≅ 16 g