With that informatio you can:
1) Write the chemical equation
2) Balance the chemical equation
3) State the molar ratios
4) Predict if precipitation occurs.
I will do all four, for you:
1) Chemical equation:
mercury(I) nitrate potassium bromide mercury(I) bromide potassium nitrate
<span>Hg2(NO3)2 + KBr → Hg2Br2 + KNO<span>3
2) Balanced chemical equation
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<span>Hg2(NO3)2 + 2KBr → Hg2Br2 + 2KNO<span>3
3) Molar ratios or proportions:
1 mol </span></span><span>Hg2(NO3)2 : 2 mol KBr : 1 mol Hg2Br2 : 2 mol KNO<span>3
4) Prediction of precipitation.
You can use the solubility rules or a table of solubilities. I found in a table of solutiblities that mercury(I) bromide is insoluble and potassium bromide is soluble, Then you can predict that the precipitation of mercury(I) bromide will occur.
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Answer:
10.76 grams
Explanation:
Given that the amount of 
is 25.0 grams.
Mass of 1 mole of = 158 grams
The number of atoms in 1 mole of is 4.
Mass of oxygen in 1 mole of = 16\times 4 = 68 grams.
Here, 158 grams of has 68 grams of oxygen
So, the amount of oxygen in 1 gram of = 68/158 grams
Therefore, the amount of oxygen in 1 gram of = 
grams
=10.76 grams
Hence, 25 grams of has 10.76 grams of oxygen.
