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200 ml of water were added to [x] ml of aqueous [y] M NH3. What is the concentration (M) of the new solution?  Your answer should have 2 decimal places.

The following species are isoelectronic: Rb+, Kr and Br-. Rank their relative sizes. (largest, medium, smallest) [medium]Kr [smallest]Rb+ [largest]Br-   

P4O6 decomposes into molecular oxygen (O2) and phosphorus (P4). Calculate the number of moles of oxygen gas produced from the decomposition of  [x] moles of P4O6. (Molar mass P4O6 = 219.9 g/mol)  Answer should include 2 digits after decimal point

HCl can produce chlorine gas and water in the presence of a catalyst and oxygen, following this reaction: 4HCl + O2 → 2Cl2 + 2H2O If [x] g of HCl are allowed to react with excess oxygen, what is the amount in grams of water produced? Your answer should have 1 decimal place. 

What is the energy in J per mol of photons of waves with wavelength [x] mm?  h= 6.626 x10-34 J s Round your answer to 3 decimal places Notes: Calculate the energy for 1 mole of photons, not just one photon.

Sulfur trioxide (SO3) is produced from the oxidation of SO2 as follows: 2 SO2 + O2  →  2 SO3 What is the percent yield if 18 g of SO3 is isolated from the reaction of  21 g of SO2  and 10 g of O2.

A solution has a pH of  [x]; what is the hydronium ion concentration? Your answer should have at least 3 decimal places.

What is the sulfate ion concentration (M) in a [x] ml solution of [M] M Al2(SO4)3? Your answer should have 2 decimal places.  

If the hydronium ion concentration is 4.3 x 10-8 M, what is the pH of the solution? Your answer should have 2 decimal places.

If the hydronium ion concentration is 7.6 x 10-9 M, what is the pH of the solution? Your answer should have 2 decimal places.