Answer:

Explanation:
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In this case, since the standard enthalpy change for a chemical reaction is stood for the enthalpy of reaction, for the given reaction:

We set up the enthalpy of reaction considering the enthalpy of formation of each species in the reaction at the specified phase and the stoichiometric coefficient:

In such a way, by using the NIST database, we find that:

Thus, we plug in the enthalpies of formation to obtain:

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<span>Ca(NO3)2 + Na2CO3 = CaCO3 + 2NaNO3
Yes a precipitate of Calcium Carbonate is formed since it is insoluble in water.
Mol Wt of Calcium Nitrate is 164. And that of Calcium Carbonate is 100.
One mole of Calcium Nitrate produces one mole of Calcium Carbonate.
i.e. 164 gms will produce 100gms of precipitate
So, 1.74gms of Calcium Carbonate will be obtained from 2.85gms Calcium Nitrate present in the original solution.</span>
Air is a mixture, Its constituens can be seperated
Answer:
B. 0.2.
Explanation:
<em>n = mass/molar mass</em>
mass of CaCO₃ = 20 g, molar mass of CaCO₃ = 100.0869 g/mol.
<em>∴ n = mass/molar mass = </em>(20 g)/(100.0869 g/mol) <em>= 0.1998 ≅ 0.2 mol.</em>
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<em>So, the right choice is: B. 0.2.</em>
To supply oxygen to the body, the respiratory system works closely with the circulatory system. As oxygen is taken in into the lungs, it travels through blood vessels, which then circulate oxygen-rich blood to cells and tissues.