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4 years ago

15 pts The drop down items have the same options for all sections labeled choose an item

Chemistry

1 answer:

tia_tia [17]4 years ago

8 0

Answer:

#8 : 21.5 L of CH₄

#9 : 36 g of H₂O

#9 : 5.4 x 10²² molecules of CO₂

Explanation:

#8 : Part 1.

Data given:

no. of moles of CH₄ = 0.960 mol

volume of CH₄ = ?

Solution

volume can be calculated by following formula

No. of moles = Volume of gas / molar volume

Rearrange the above equation

Volume of gas = No. of moles x molar volume . . . . . . (1)

Where

molar volume = 22.4 L/mol

Put values in equation 1

Volume of gas = 0.960 mol x 22.4 L/mol

Volume of gas = 21.5 L

So,

By calculation 0.960 moles have 21.5 L volume of CH₄

_______________

#9 : Part 2.

Data given:

no. of moles of H₂O = 2.0 mol

mass of H₂O = ?

Solution

volume can be calculated by following formula

No. of moles = mass in grams / molar mass

Rearrange the above equation

mass in grams = No. of moles x molar mass . . . . . . (2)

Where

molar mass of H₂O = 2 (1) + 16

molar mass of H₂O = 18 g/mol

Put values in equation 2

mass in grams = 2.0 mol x 18 g/mol

mass in grams = 36 g

So,

By calculation 2.0 moles have 36 g mass of H₂O

________________

#10 : Part 3.

Data given:

volume of CO₂ = 2 L

no. of molecules of CO₂ = ?

Solution

First we have to find out number of moles of CO₂

Following formula will be used

No. of moles = Volume of gas / molar volume

Where

molar volume = 22.4 L/mol

Put values in above equation

No. of moles = 2 L / 22.4 L/mol

No. of moles = 0.0893 mol

So,

No. of moles of CO₂ = 0.0893 mol

Now

we will calculate number of molecules by using following formula

No. of moles = no. of molecules / Avogadro's number

Rearrange the above equation

no. of molecules = No. of moles x Avogadro's number . . . . . . (3)

Where

Avogadro's number = 6.022 x 10²³

Put values in above equation 3

no. of molecules = 0.0893 mol x 6.022 x 10²³

no. of molecules = 5.4 x 10²²

So,

By calculation 2 L of CO₂ have 5.4 x 10²² molecules of CO₂

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Question 1(Multiple Choice Worth 3 points)

Bingel [31]

1) Answer:

moles of oxygen (n) = 1.86 moles

Explanation:

according to Boyle's law the formula to solve this problem is:

PV=nRt

when P is the pressure which equal 1.25 atm

and V is the volume which equal 37.5 L

n is the number of moles which we need to calculate it

R is constant which equal 0.082

t is the temperature in kelvin

By substitution:

1.25*37.5 = n * 0.082 * 307

So n = 1.86 moles

2) Answer:

the volume of oxygen gas = 34 L

Explanation:

at standard temperature and pressure (STP) 1 mole of gas will equal = 22.4L

So when we have 1.5 moles of oxygen at standard temperature and pressure (STP) so we will estimate it like that

1.5 moles *22.4 L/ 1 mole = approximately 34 L

3) Answer:

The volume of H2 = 2.29 L

Explanation:

according to the Balanced equation we can see that the molar ratio between Zn and H2 1 : 1

so to know the number of moles of H2 we will get it for Zn first :

number of moles Zn = mass of Zn / molar mass Zn

= 5.98 / 65.39 =0.0914 moles

so number of moles H2 = 0.09 moles

by substitution in the following formula:

PV = nRT

0.978 * V = 0.09 * 0.082 * 298

so The volume of H2 = 2.29 L

4) Answer:

Volume of O2 = 1.4 L

Explanation:

first we have to balance the equation:

2Na2O2 +2CO2 → 2Na2CO3 + O2

2 mole CO2 give 1 mole of O2 so the molar ratio is 2:1

at STP 1 mole of gas will equal = 22.4 L

??? moles of CO2 = 2.8

n CO2 = 0.125 moles so n O2 = 0.125 /2 = 0.0625 moles

so when 1 mole of as = 22.4

0.0625 moles O2 = ???

Volume of O2 =0.0625 moles * 22.4 L/ 1 mole

= 1.4 L

5) Answer:

the initial quantity of sodium metal used = 17.2 gram

Explanation:

at STP 1 mole of gas will equal = 22.4 L

so moles of H2 equal ?? when 8.40 liters of H2 gas were produced

so moles of H2 = 8.4/22.4 =0.375 moles

and according to the balanced equation the molar ratio between H2 ans Na is 1 : 2

so number of moles for Na = 0.375 *2 = 0.75 moles

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6) Answer:

False

Explanation:

because STP means standard temperature and pressure. and the Standard temperature must be 273 K and the standard pressure must be 1 atm but in the question the temperature is 298 K not 273 K so , It is not a standard temperature

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22.4 liters

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