icecalm:
the question is not well framed and infinite number of answers do exit for Z for the values you choose for X and Y. From the options (A) 4 is an answer to the question when X=4 and Y=5

alright, thanks.

icecalm:
(1) The Atomicity of any element is the number of atoms of that element that will make a molecule of the element, i.e the atomicity of oxygen (O₂) is 2, while that of ozone(O₃) is 3. Sulphur exist in it molecule state as S₈ and it atomicity is 8. C

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(2) NB: This question require knowledge of stoichiometry.
From the given data we could determine which law of chemical combination the reaction obey. First we have to write a balanced equation for the reaction.

N₂ + O₂ ——> NO + NO

Now, let us inspect the above equation to see if it's correct with the data given.
NB: The equation already failed in the R.H.S; only one type of oxide is given.

For a single mole of Nitrogen gas, half,one and two moles of oxygen gas is required to form Nitrogen peroxide, Nitrogen(ii)oxide and Nitrogen(iv)oxide respectively. dinitrogen tetraoxide (N₂O₄) may also be formed with two moles of oxygen gas.
The next step is to compare the mass of the oxides given with the mass you will obtain by calculating the mass of the above listed oxides that will likely be formed from the given mass of Nitrogen gas.
Mass of N₂=0.8
Moles of N₂ = 0.8/28mol

From the above reaction, 1mole of N₂ will form 1mol of either of the two oxides with oxygen. Therefore, 0.8/28mol of N₂ will form 0.8/28mol of either of the two oxides.
Mass of the oxides that will be formed with 0.8/28mol of N₂:
We will be using,
Atomic mass=mole×molar mass

Nitrogen peroxide(N₂O) = 0.8/28×44 =1.26g

Nitrogen(ii)oxide(NO) =0.8/28×30= 0.86g

Nitrogen(iv)oxide (NO₂)= 0.8/28×46=1.31g

dinitrogen tetraoxide (N₂O₄)= 0.8/28×92= 2.63g

By comparison, the oxides likely to be formed are NO and NO₂.
we proceed to write the balanced equation, 2N₂ + 3O₂ ——> 2NO₂ + 2NO.
(NB: we balance the coefficients by inspection)
A.... Law of multiple proportion, since the O combine with N in simple multiples.
B.... Nitrogen(iv)oxide and Nitrogen(ii)oxide
C....same mass of the oxides as those given in the question would be formed when 0.8g of Nitrogen gas is mixed with 2.89g of Oxygen gas and only 1.37g of the Oxygen gas will react, while the others will remain as excess.

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(3) first we write a balanced equation for the reaction;
C + O₂ ——> CO₂
From the equation 1mole of carbon(vi)oxide will be produce from 1mole of Oxygen gas.

Molar volume of gas at stp 22.4dm³ and this is equivalent to 22400cm³

Volume of oxygen gas required to produce 5mol of CO₂= 22400×5 = 112000cm³. A

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I WILL EXPLAIN Q 4-10 TOMORROW. walanter, abuhubaidah, geoflavor and others

Why is H3PO4 weak acid since it can ionize completely in water and has a high concentration of hydrogen ions. i.e H3PO4-------3H+ + PO4

Mrbehave:
Why is H3PO4 weak acid since it can ionize completely in water and has a high concentration of hydrogen ions. i.e H3PO4-------3H+ + PO4

The acid does not hydrolyze completely and easily as you have written in that equation

strong acids have pKa value less than -2 while weak acids have pKa values greater than -2. the more positive a pKa value is the less strong the acid will be.

HCL hydrolyze in water by dissociation with the formation of H⁺, when we take the ratio of the concentration of dissociated acid to non dissociated acid we obtain the Ka constant of dissociation of the acid at the equilibrium state. for HCl the value is large enough to give (–ve) value of pKa= –logK_a= –7

the more positive the pKa of an acid the less stronger the acid is.

H3PO4 has a pKa1= 2.1 this is for the dissociation of the first H+

H3PO4 + H2O ––> H2PO4- + H3O+ pKa= 2.1

the positive pKa of the acid is due to its structure. the H3PO4 molecule has all the 4 oxygen atoms attached to a center P this make the compound less polar by the cancelling effect of each opposite Oxygen atom. the molecule is made a bit polar by the 3 hydrogen atoms attached to the oxygen atoms in the molecule. the side opposite the oxygen with no hydrogen atom is more polar and dissociate more easily compared to the other two. after first dissociation the pKa value increase for a second dissociation it about 7.2 and 12.3 for a third dissociation. the reason is because of the increasing negative charge ion, which reduce dissociation. HI is the second most strongest acid.

1moldm3 of H3PO4 will produced extremely less amount of H+ in a solution compare to 1moldm3 of HCl. this attribute confirm the definition of strong and weak acid. strong, ionise completely and weak ionise incompletely

icecalm:
The acid does not hydrolyze completely and easily as you have written in that equation

strong acids have pKa value less than -2 while weak acids have pKa values greater than -2. the more positive a pKa value is the less strong the acid will be.

HCL hydrolyze in water by dissociation with the formation of H⁺, when we take the ratio of the concentration of dissociated acid to non dissociated acid we obtain the Ka constant of dissociation of the acid at the equilibrium state. for HCl the value is large enough to a give (–ve) value of pKa= –logK_a= –7

the more positive the pKa of an acid the less stronger the acid is.

H3PO4 has a pKa1= 2.1 this is for the dissociation of the first H+

H3PO4 + H2O ––> H2PO4- + H3O+ pKa= 2.1

the positive pKa of the acid is due to its structure. the H3PO4 molecule has all the 4 oxygen atoms attached to a center P this make the compound less polar by the cancelling effect of each opposite Oxygen atom. the molecule is made a bit polar by the 3 hydrogen atoms attached to the oxygen atoms in the molecule. the side opposite the oxygen with no hydrogen atom is more polar and dissociate more easily compared to the other two. after first dissociation the pKa value increase for a second dissociation it about 7.2 and 12.3 for a third dissociation. the reason is because of the increasing negative charge ion, which reduce dissociation. HI is the second most strongest acid.

1moldm3 of H3PO4 will produced extremely less amount of H+ in a solution compare to 1moldm3 of HCl. this attribute confirm the definition of strong and weak acid. strong, ionise completely and weak ionise incompletely

Gud one.