Answer:
3
Explanation:
Subscript basically tells you the number of element or ions present in a compound. In this case the subscript of carbon which is 3 denotes that only three carbon atoms is present in the compound.
The correct answers are as follows:
1. MgSO4 + 2NH4OH = [NH4]2SO4 + Mg[OH]2.
This chemical equation implies that, one molecule of magnesium sulphate react with two molecules of ammonium hydroxide to give rise to one molecule of ammonium sulphate and one molecule of magnesium hydroxide.
2. The reaction between magnesium sulphate and ammonia is a DOUBLE REPLACEMENT REACTION.
A double replacement reaction is a type of reaction in which the two chemical substances which take part in the reaction switch their ions in such a way that two new products are formed. In the reaction of magnesium sulphate and ammonia, the magnesium sulphate gives its SO4 ion to ammonia and take the OH ion of the ammonia instead.
3. The epsom salt and the ammonia reacted. This is made obvious by the chemical reaction which was generated by their combination. On the edge of the penny used, one can see that there is a colour change, this shows that a chemical reaction occur.
<u>Answer:</u> The mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.
<u>Explanation:</u>
The given chemical reaction follows:
We know that:
Molar mass of nitrogen gas = 28 g/mol
We are given:
Enthalpy change of the reaction = 14.2 kJ
To calculate the mass of nitrogen gas reacted, we use unitary method:
When enthalpy change of the reaction is 66.4 kJ, the mass of nitrogen gas reacted is 28 grams.
So, when enthalpy change of the reaction is 14.2 kJ, the mass of nitrogen gas reacted will be = 
Hence, the mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.
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