# Chemistry

Q1. A 0.5 g mixture of Cu2O and CuO contain 0.425 g Cu. What is the mass of CuO in the mixture?

Q2. A chemist wants to prepare 0.5 M HCl. The label of a commercial hydrochloric acid shows that S.G. =1.18 and concentration of HCl was 37%. Calculate the volume of commercial hydrochloric acid dose the chemist requires to make up 1.5 L of the dilute acid.

Q3. Relate the rate of decomposition of NO2 to the rate of formation of O2 for the following reaction.

Thanks

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1. #2. Determine the molarity (M) of the concentrated acid.
1000 mL x 1.18 g/mL x 0.3 x (1/36.5) = ?M My estimated value for this is 12M but you need to refine the answer.
Then use the dilution formula of
mL1 x M1 = mL2 x M2
mL1 x 12 = 1,500 x 0.5
Solve for mL of the 12 M HCl to use.
To prepare you drop ? of the conc HCl into a 1.5 volumetric flask and make to the mark with distilled water. Mix thoroughly and stopper.

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2. #1. I work these as two equations and solve them simultaneously.
Let X = mass CuO
and Y = mass Cu2O
--------------------
equation 1 is X + Y = 0.5

Equation 2 comes from this. The grams copper from CuO + copper from Cu2O = 0.425g. With MM standing for molar mass and AM for atomic mass:
Grams Cu from CuO is (AM Cu*X/MM CuO)

Grams Cu from Cu2O is (2*AM Cu*Y/MM Cu2O)

Put that together for equation 2 as follows:
(AM Cu*X/MM CuO) + (2*AM Cu*Y/MM Cu2O) = 0.425

Solve equation 1 and equation 2 for X = grams CuO
Post your work if you get stuck.

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3. Thank you very much!

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4. for #2
Why the equation need to x 1000 ?
Thank

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5. 0.212 g CuO

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6. #1=0.216GRAMS

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