Answer: is equal to
Explanation: According to law of conservation of mass, the mass can neither be created nor be destroyed. Thus the mass of products must be equal to the mass of reactants.
In order to have same mass on both sides of the chemical equation, the number of atoms of each element must be same in reactants as well as products.
<u>Answer:</u> The amount of heat released when 0.211 moles of 
reacts is 554.8 kJ
<u>Explanation:</u>
The chemical equation for the reaction of 
with oxygen gas follows:
The equation for the enthalpy change of the above reaction is:
![\Delta H_{rxn}=[(5\times \Delta H_f_{(B_2O_3(s))})+(9\times \Delta H_f_{(H_2O(l))})]-[(2\times \Delta H_f_{(B_5H_9(l))})+(12\times \Delta H_f_{(O_2(g))})]](https://tex.z-dn.net/?f=%5CDelta%20H_%7Brxn%7D%3D%5B%285%5Ctimes%20%5CDelta%20H_f_%7B%28B_2O_3%28s%29%29%7D%29%2B%289%5Ctimes%20%5CDelta%20H_f_%7B%28H_2O%28l%29%29%7D%29%5D-%5B%282%5Ctimes%20%5CDelta%20H_f_%7B%28B_5H_9%28l%29%29%7D%29%2B%2812%5Ctimes%20%5CDelta%20H_f_%7B%28O_2%28g%29%29%7D%29%5D)
We are given:
Putting values in above equation, we get:
![\Delta H_{rxn}=[(2\times (-1272))+(9\times (-285.4))]-[(2\times (73.2))+(12\times (0))]\\\\\Delta H_{rxn}=-5259kJ](https://tex.z-dn.net/?f=%5CDelta%20H_%7Brxn%7D%3D%5B%282%5Ctimes%20%28-1272%29%29%2B%289%5Ctimes%20%28-285.4%29%29%5D-%5B%282%5Ctimes%20%2873.2%29%29%2B%2812%5Ctimes%20%280%29%29%5D%5C%5C%5C%5C%5CDelta%20H_%7Brxn%7D%3D-5259kJ)
To calculate the amount of heat released for the given amount of , we use unitary method, we get:
When 2 moles of reacts, the amount of heat released is 5259 kJ
So, when 0.211 moles of will react, the amount of heat released will be = 
Hence, the amount of heat released when 0.211 moles of reacts is 554.8 kJ
Answer:
C. Hair dryer
Explanation:
Alternating Current
The other kind of electricity is called alternating current, or AC. Power plants produce this
type of electricity. It is carried by large power lines from the plant to your home. When you
plug a TV, a lamp, or a hair dryer into the wall socket, you are using this type of electricity.
Answer:
0.271 M NO₃⁻
Explanation:
To find the molarity of the nitrate ion (NO₃⁻), you need to (1) convert grams to moles (via molar mass), then (2) convert moles Al(NO₃)₃ to moles NO₃⁻, then (3) convert mL to L, and then (4) calculate the molarity. When (Al(NO₃)₃) dissolves in water, it dissociates into 3 nitrate ions. The final answer should have 3 sig figs.
(Steps 1 + 2)
Molar Mass (Al(NO₃)₃): 26.982 g/mol + 3(14.007 g/mol) + 9(15.998 g/mol)
Molar Mass (Al(NO₃)₃): 212.985 g/mol
1 Al(NO₃)₃ = 1 Al³⁺ and 3 NO₃⁻
6.25 g Al(NO₃)₃ 1 mole 3 moles NO₃⁻
------------------------- x ----------------- x ----------------------- = 0.0880 moles NO₃⁻
212.985 g 1 mole Al(NO₃)₃
(Steps 3 + 4)
325.0 mL / 1,000 = 0.3250 L
Molarity = moles / volume
Molarity = 0.0880 moles / 0.3250 L
Molarity = 0.271 M
Answer:
18 DAYS IS THE HALF LIFE OF THE RADIOISOTOPE.
Explanation:
Using the formula
Nt = No * (1/2)^t/t1/2
where;
Nt = amount remaining = 25 g
No = Initial amounrt of the radioisotope = 50 g
t = time elapsed = 18 days
t1/2 = half life = unknown
Substitute the values into the equation and obtain the half life of the radioisotope;
Nt = No * (1/2) ^t/t1/2
25 = 50 * (1/2) ^18/t1/2
25 /50 = (1/2)^18/ t1/2
1/2 = (1/2)^18/t1/2
1/2)^1 = (1/2)^18/t1/2
1 = 18/t1/2
t1/2 = 18 days.
So therefore the half life of the radioisotope is 18 days.
