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Answer:
7.5 g of hydrogen gas reacts with 50.0 g oxygen gas to form 57.5 g of water.
Explanation:
Here we have the check if the mass of the reactants is equal to the mass of the products.
Reactants

Products

The data is consistent with the law of conservation of matter.
Reactants

Products

The data is not consistent with the law of conservation of matter.
Reactant

Products

The data is not consistent with the law of conservation of matter.
Only the first data is consistent with the law of conservation of matter.
Answer:
Heat transfer in step 2 = 47.75 J
Explanation:
Internal energy = heat + work done
U = Q + W
In a cyclic process the total internal energy change of the system = 0.
In the process there are two steps. The total heat exchange in the process is the sum of heat exchanges in the two processes.
We have to find the heat exchange in step 2.
In step 1,
W = 1.25 J Q = -37 J
= -37 + 1.25 = -35.75 J
In step 2, the internal energy change will be negative of that in step 1.
U = 35.75 J
W = -12 J
U = Q + W
35.75 = Q -12
Q = 47.75 J
Heat transfer in step 2 = 47.75 J
Their atomic number increases