Answer:
Na₂CO₃ · 10H₂O
Explanation:
The formula for sodium carbonate hydrate is:
Na₂CO₃ · xH₂O
The unknown "x" is the number of water molecules contained in the hydrate.
To find "x" we have to use the hydrogen percentage in the sample, 7.05 % H.
First we calculate the molecular weight of Na₂CO₃ · xH₂O:
molecular weight of Na₂CO₃ · xH₂O = 23 × 2 + 12 + 16 × 3 + 18x
molecular weight of Na₂CO₃ · xH₂O = 106 + 18x g/mole
Now we devise the fallowing reasoning tanking in account 1 mole of Na₂CO₃ · xH₂O:
if in 106 + 18x grams of Na₂CO₃ · xH₂O we have 2x grams of hydrogen
then in 100 grams of Na₂CO₃ · xH₂O we have 7.05 grams of hydrogen
106 + 18x = (100 × 2x) / 7.05
106 + 18x = 28.4x
106 = 28.4x - 18x
106 = 10.4x
x = 106 / 10.4
x = 10.2 ≈ 10
The formula for the washing soda is Na₂CO₃ · 10H₂O.
This technique can be used to make pure crystals of a soluble salt.
The burette is filled with hydrochloric acid.
A known quantity of alkali (say 50 cm3 sodium hydroxide)
is released from a pipette into the conical flask.
The tap on the burette is turned open to allow
the acid to be added drop by drop into the alkali.
The alkali contains an indicator (phenolphthalein)
which is pink in an alkali and colorless in an <span>acid.
</span>
When enough acid has been added to neutralize
the alkali, the indicator changes from
pink to colorless. This is the end point of the titration.
The titration<span> can be repeated using the </span><span>same amounts
</span><span>of </span>acid<span> and </span>alkali<span> but </span>without<span> the </span>indicator.
<span>Pure salt</span> crystals<span> which are </span>free<span> from </span><span>indicator
</span><span>can then be crystallized </span><span> from the </span>neutral<span> solution.</span>
There are 1000 mg in 1 gram.
3.76/1000 = 0.00376
10^-3 = 0.001
0.001 x 3.76 = 0.00376
Answer is
3.76 x 10^-3
When heat energy at a constant pressure = the change of enthalpy
ΔH = Q
and when the internal energy of an ideal gas formula is:
ΔH = n.Cp.ΔT
and when Cp = (5/2) R at a constant pressure of a monatomic ideal gas
∴Q = n.(5/2).R.ΔT
∴ ΔT = Q / [n.(5/2).R]
when Q is the heat required = 43.08 J (given)
and n is no.of moles = mass / molar mass
= 1.1 g / 39.948 g/mol
= 0.0275 moles
and R is gas constant = 8.314472J/mol K
by substitution:
ΔT = 43.08 J / (0.0275moles *(5/2) * 8.314472 J/mol K
= 76.76 K
In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions.
Hope This Helps! Have A Nice Day!
