Answer:
3.52g
Explanation:
Zr = 90 g/mol
Si = 28 g/mol
O = 16 g/mol
ZrSiO4 = 90 + 28 + (16* 4) = 182g/mol
Mass = Numberof moles * Molar mass
Mass = 1mol * 182g/mol = 182g
In one mole of ZrSiO4, there are 4 oxygen atoms, hence the mass is given as;
4 * 16 = 64g
Hence, 64g of oxygen is present in 182g of ZrSiO4.
10g would contain x
64 = 182
x = 10
x = ( 10 * 64 ) / 182
x = 640 / 182 = 3.52g
Answer: The change in enthalpy will be -13.
Explanation:-
Endothermic reactions are those in which heat is absorbed by the system and exothermic reactions are those in which heat is released by the system.
for Endothermic reaction is positive and
for Exothermic reaction is negative.

When 1 mole of A combining with 1 mole of B to produce 3 moles of C
Thus as the stoichiometry has got half of the original , enthalpy of the reaction will also get half.
Thus for reaction :

Thus the change in enthalpy will be -13.
Answer:
One of the bonds in nitrate is shorter than the other two.
Explanation:
We would firstly need to draw the Lewis structure for nitrate anion. To do this, let's follow the standard steps:
- calculate the total number of valence electrons: five from nitrogen, each oxygen contributes 6, so a total of 18 from oxygen atoms, as well as one from the negative charge, we have a total of 24 valence electrons;
- assign the central atom, usually this is the atom which is single; in this case, we have nitrogen as our central atom;
- assign single bonds to all the terminal atoms (oxygen atoms);
- assign octets to the terminal atoms and calculate the number of electrons assigned;
- the number of electrons assigned is 24, so no lone pairs are present on nitrogen;
- calculate the formal charges: each oxygen has a formal charge of -1 (formal charge is calculated subtracting the sum of lone pair electrons and bonds from the number of valence electrons of that atom); nitrogen has a formal charge of +2;
- nitrogen doesn't have an octet as well, so we'll both minimize its formal charge and make it obtain an octet if we make one double bond N=O.
Therefore, we may have 3 resonance structures, as this double bond might be formed with any of the 3 oxygen atoms.
By definition, double bonds are shorter than single ones, so one of the bonds is shorter than the other two.