Two technicians are discussing testing coolant for proper pH. Technician A says that coolant has a pH above 7 when new and becom
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6.52 × 10⁴ L. (3 sig. fig.)
<h3>Explanation</h3>Helium is a noble gas. The interaction between two helium molecules is rather weak, which makes the gas rather "ideal."
Consider the ideal gas law:
,
where
is the pressure of the gas,
is the volume of the gas,
is the number of gas particles in the gas,
is the ideal gas constant, and
is the absolute temperature of the gas in degrees Kelvins.
The question is asking for the final volume of the gas. Rearrange the ideal gas equation for volume:
.
Both the temperature of the gas, , and the pressure on the gas changed in this process. To find the new volume of the gas, change one variable at a time.
Start with the absolute temperature of the gas:
,
.
The volume of the gas is proportional to its temperature if both and
stay constant.
- consider
.
Now, keep the temperature at and change the pressure on the gas:
,
.
The volume of the gas is proportional to the reciprocal of its absolute temperature if both
and
stays constant. In other words,
(3 sig. fig. as in the question.).
See if you get the same result if you hold constant, change
, and then move on to change
.
Answer:
0.88g
Explanation:
The reaction equation:
2NaI + Cl₂ → 2NaCl + I₂
Given parameters:
Mass of Sodium iodide = 2.29g
Unknown:
Mass of NaCl = ?
Solution:
To solve this problem, we work from the known to the unknown.
First find the number of NaI from the mass given;
Number of moles =
Molar mass of NaI = 23 + 126.9 = 149.9g/mol
Now insert the parameters and solve;
Number of moles = = 0.015mol
So;
From the balanced reaction equation;
2 moles of NaI produced 2 moles of NaCl
0.015mole of NaI will produce 0.015mole of NaCl
Therefore;
Mass = number of moles x molar mass
Molar mass of NaCl = 23 + 35.5 = 58.5g/mol
Now;
Mass of NaCl = 0.015 x 58.5 = 0.88g