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3 years ago

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Mass and energy are conserved Question 13 options: A) only in chemical changes. B) always in physical changes and sometimes in c

hemical changes. C) only in physical changes. D) in chemical changes and physical changes.

1 answer:

Roman55 [17]3 years ago

3 0

Answer:

B

Explanation:

sometimes it can change chemically but not all the time.

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Suppose 13.6 g of barium nitrate is dissolved in 300. mL of a 0.40M aqueous solution of sodium chromate. Calculate the final mol

Elis [28]

Answer:

The molarity of barium cation in the solution is 0.173 M

Explanation:

Step 1: The balanced equation

Ba(NO3)2(aq) + Na2CrO4 (aq) → BaCrO4(s) + 2NaNO3(aq)

Step 2: Data given

Mass of Barium nitrate = 13.6 grams

Volume of 0.40M sodium chromate = 300 mL

Step 3: Calculate moles of Ba(NO3)2

Moles = mass / molar mass

Moles = 13.6 grams / 261.34 g/mol

Moles = 0.052 moles

Step 4: Calculate moles of Na2CrO4

Moles = Molarity * Volume

Moles Na2CrO4 = 0.40 * 0.3L

Moles Na2CrO4 = 0.12 moles

Step 5: Calculate limiting reactant

Na2CrO4 is in excess so all of Ba(NO3)2 will be consumed and reacts to form BaCrO4(s) in the form Ba2+

Step 6: Calculate moles of Ba2+

n(Ba2+)=n(BaCrO4) =n(Ba(NO3)2 = 0.0520 moles

Step 7: Calculate molarity of Ba2+

C=n/v so C(Ba2+)=0.0520/0.300 = 0.173 M

The molarity of barium cation in the solution is 0.173 M

4 0

3 years ago

Which element requires the least i.e. potassium or gallium why

-Dominant- [34]

Answer:

Potassium

General Formulas and Concepts:

<u>Chem</u>

Reading a Periodic Table
Periodic Trends
Ionization Energy - energy required to remove an electron from a given element
Coulomb's Law
Shielding Effect
Z-effective and Forces of Attraction

Explanation:

The Periodic Trend for 1st Ionization Energy is increasing up and to the right. That means He would have the highest I.E and therefore take the most amount of energy to remove an electron.

Potassium and Gallium are both in Period 4. Potassium is element 19 and Gallium is element 31.

Potassium's electron configuration is [Ne] 4s¹ and Gallium's electron configurations is [Ne] 4s²3d¹⁰4p¹. Since both are in Period 4, they have the same number of core e⁻. Therefore, the shielding effect is the same.

However, since Gallium is element 31, it has 31 protons compared to Potassium, which is element 19 and has 19 protons. Gallium would have a greater Zeff than Potassium as it has more protons. Therefore, the FOA between the electrons and nucleus of Ga is much stronger than that of K. Thus, Ga requires <em>more</em> energy to overcome those FOA to remove the 4p¹ e⁻. Since K has less protons, it will have a smaller Zeff and thus less FOA between the e⁻ and nucleus, requiring <em>less</em> energy to remove the 4s¹ e⁻.

7 0

3 years ago

At STP, which gas sample has a volume of 11.2 liters?

Natasha2012 [34]

Answer:

0.500 moles of CO2 has a volume of 11.2 L at STP (option B)

Explanation:

Step 1: Data given

Volume of a gas at STP = 11.2 L

STP: Pressure = 1 atm and temperature = 273 K

Step 2: Calculate volume

p*V= n*R*T

V = (n*R*T)/p

⇒with V = the volume of the gas = TO BE DETERMINED

⇒with n = the number of moles of the gas

⇒with R = the gas constant = 0.08206 L*atm/mol*K

⇒with T = the temperature = 273 K

⇒with p = the pressure of the gas = 1 atm

A ) 0.250 mole of NH3

V = (0.250 * 0.08206 * 273) / 1

V = 5.6 L

B ) 0.500 mole of CO2

V = (0.500 * 0.08206 * 273) / 1

V = 11.2 L

C ) 0.750 mole of NH3

V = (0.750 * 0.08206 * 273) / 1

V = 16.8 L

D) 1.00 mole of CO2

V = (1.00 * 0.08206* 273) / 1

V = 22.4 L

0.500 moles of CO2 has a volume of 11.2 L at STP (option B)

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4 years ago

Please balance xe+f2=xef6

Marysya12 [62]

If’s chemistry it would be like this- Xe=1 and F=2/Xe=1 and F=6 so, to balance Xe=1 and F=[3x2]/Xe=1 and F=6.

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3 years ago

you turn on a lamp.The amount of light energy released by the light bulb is less than the amount of electrical energy that flows

valentinak56 [21]

A) some energy is converted to heat

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3 years ago