Answer:
27%
Explanation:
Hello,
The following information is missing, but I found it: "1.92 g of sodium sulfate is produced from the reaction of 4.9 g of sulfuric acid and 7.8 g of sodium hydroxide" so the undergoing chemical reaction is:

Now, to compute the percent yield, we must first establish the limiting reagent to subsequently determine the theoretical yield of sodium sulfate because the real (1.92g) is already given, thus, we consider the following procedure:

- The moles of sodium hydroxide that completely react with 0.05 moles of sulfuric acid are:

As this number is higher than the previously computed 0.05 moles of available sulfuric acid, one states that the sulfuric acid is the limiting reagent. Now, the theoretical grams of sodium sulfate are found via:

Finally, the percent yield turns out into:

%
Best regards.
Heat would be required : 1,670 J
<h3>Further explanation</h3>
Given
mass of H₂O=5 g
Required
Heat to melt
Solution
The heat to change the phase can be formulated :
Q = m.Lf (melting/freezing)
Lf=latent heat of fusion
The heat of fusion for water at 0 °C : 334 J/g
Input given values in formula :

Answer: 325 mg
Explanation:
Grains ---> ounces -----> pounds -----> grams -----> mg
5 gr x (0.00229 oz / 1 gr) x (1 lb / 16 oz) x (454 g / 1 lb) x (1000 mg / 1 g) = 325 mg
Hey there !
<span>Balanced equation:
1 MgS +1 Na2O = 1 Na2S + 1 MgO
</span>
MgS = 1
Na2O = 1
Na2S = 1
MgO = 1
Answer D