CHEMISTRY MIDDLE SCHOOL

1. If you have a 1-g sample of Po-218, how many grams would youhave after 6 minutes? After 18 minutes?
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Answers

Answer 1
Answer:

Answer:

a) 0.25 g b) 0.01542 g

Explanation:

Half life of Po-218 = 3.04 minutes

initial mass = 1 g

after 3.04 minutes it will remain 0.5 g

after another 3.04 minutes it will remain 0.25 g

After 6 minutes it will remain approx 0.25 g

B) after another 3.04 minutes it will remain 0.125 g

after another 3.04 minutes it will remain 0.0625 g

after another 3.04 minutes it will remain 0.03125 g

after another 3.04 minutes it will remain 0.015625 g

After 18 minutes it will remain approx 0.01542 g

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Use bond energies to calculate the enthalpy change for the following reaction. H2(g) + CO2(g) ⟶ H2O(g) + CO(g)

please help!!!

Answers

The enthalpy change for the given reaction is 36kJ/mol
Answer is 36kj/mol same question thank you

Gasoline is a mixture of compounds. A gasoline sample was found to be 2.851% (by mass) octane (C₈H₁₈). 482.6 g of gasoline is combusted to produce gaseous carbon dioxide and gaseous water.Write out the balanced combustion reaction of octane with oxygen gas to form carbon dioxide and water. Submit an image of the balanced reaction.
Show all work.

Answers

Answer:

See below.

Explanation:

The mass of octane in the sample of gasoline is 0.02851 * 482.6 =  13.759 g of octane.

The balanced equation is:

2C8H18(l)  +  25O2(g) ---->  16CO2(g)  +   18H2O(g)

From the equation, using  atomic masses:

228.29 g of  octane forms 704 g of CO2 and 324.3 g of H2O

So the mass of CO2 formed from the combustion of 13.759 g of octane = (704 * 13.759) / 228.29

= 42.43 g of CO2.

Amount of water = 324.3 * 13.759) / 228.29

= 19.55 g of H2O.

7. An 8.92 kilogram bar of steel at 25°C is heated in order to shape it into a beam. The amount of heat energytransferred to the steel is found to be 5.82 x 103 kJ. If the specific heat capacity of steel is 0.51 op what was the
change in the temperature of the steel?​

Answers

Answer:

1279 °C

Explanation:

Data Given:

Amount of Heat absorb = 5.82 x 10³ KJ

Convert KJ to J

1 KJ = 1000 J

5.82 x 10³ KJ = 5.82 x 10³ x 1000 = 5.82 x10⁶ J

mass of sample = 8.92 Kg

Convert Kg to g

1 kg = 1000 g

8.92 Kg = 8.92 x 1000 = 8920 g

Cs of steel = 0.51 J/g °C

change in temperature = ?

Solution:

Formula used

             Q = Cs.m.ΔT

rearrange the above equation to calculate the mass of steel sample

             ΔT =  Q / Cs.m  .... . . . . . (1)

Where:

Q = amount of heat

Cs = specific heat of steel = 0.51 J/g °C

m = mass

ΔT = Change in temperature

Put values in above equation 1

                ΔT = 5.82 x10⁶ J / 0.51  (J/g °C) x 8920 g

                ΔT = 5.82 x10⁶ J /4549.2 (J/°C)

                ΔT = 1279 °C            

So,

change in temperature = 1279 °C

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(2) gold (4) zinc

Answers

(4) Zinc is correct answer. Others don't react at room temperature with HCl because their reactivity (capability to react) is quite low.
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What is the empirical formula of sulphur dioxide which contains 50% by mass of sulphur​

Answers

Answer:

Empirical formula is SO2.

Explanation:

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Dividing by the atomic masses of sulphur and oxygen:

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O = .50 / 16 = 0.3125

Ratio of S: O =     0.015625/ 0.015625 to 0.3125/ 0.015625    

= 1:2.

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Answers

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