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zavuch27 [327]
3 years ago
8

Students at Allendale High School were tardy most often for fourth hour, right after lunch. Therefore, the

Chemistry
1 answer:
mote1985 [20]3 years ago
7 0
The answer should be true because once they took away open campus for lunch that is when the tardiness for students went way down
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When a chemical reaction occurs, what always stays the same between reactants and products?
BlackZzzverrR [31]
The total number of atoms remains unchanged, <em>always.</em> But the chemical properties change :)

please rate brainliest! thanks!
7 0
3 years ago
Sodium tripolyphosphate is used in detergents to make them effective in hard water. calculate the oxidation number of phosphorus
Fed [463]
Step 1:
           
Write molecular Formula,

                                                Na₅P₃O₁₀
Step 2:
         
Assign Oxidation number to Na (which is +1) and O (which is -2), and X (unknown) for P.
                                               (+1)₅ + (X)₃ + (-2)₁₀  = 0

Zero means overall charge on molecule is zero (Neutral).

Step 3:
           
Now solve for X,
                                               (+5) + (X ÷ 3) + (-20)  =  0

                                                X ÷ 3  =  -5 + 20
                                
                                                X ÷ 3  =  +15

                                                      X  =  +15 ÷ 3

                                                      X  =  +5

Result:
           Oxidation number of P is +5.                                 
3 0
3 years ago
alculate the standard enthalpy of formation of ethanoic acid given that the standard enthalpy of combustion for carbon is –394 k
agasfer [191]

Answer:

The standard enthalpy of formation of ethanoic acid is -484 kJ/mol.

Explanation:

C(g)+O_2(g)\rightarrow CO_2(g),\Delta H_{1, comb}=-394 kJ/mol...[1]

H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l),\Delta H_{2, comb}=-286 kJ/mol..[2]

CH_3COOH(l)+2O_2(g)\rightarrow 2CO_2(g)+2H_2O(l),\Delta H_{3, comb}=-876 kJ/mol..[3]

The standard enthalpy of formation of ethanoic acid :

2C(g)+2H_2(g)+O_2(g)\rightarrow CH_3COOH, \Delta H_{4}=?..[4]

Using Hess's law to calculate :

2 × [1] + 2 × [2] - [3] = [4]

\Delta H_4=2\times (-394 kJ/mol)+2\times (-286 kJ/mol) - (-876 kJ/mol)

=\Delta H_4=-484 kJ/mol

The standard enthalpy of formation of ethanoic acid is -484 kJ/mol.

5 0
3 years ago
You have 50 ml of a complex mixture of weak acids that contains some HF (pKa = 3.18) and some HCN (pKa = 9.21). Which is larger,
telo118 [61]

Answer:

\frac{[F^{-}]}{[HF]} is larger

Explanation:

pK_{a}=-logK_{a} , where K_{a} is the acid dissociation constant.

For a monoprotic acid e.g. HA, K_{a}=\frac{[H^{+}][A^{-}]}{[HA]} and \frac{[A^{-}]}{[HA]}=\frac{K_{a}}{[H^{+}]}

So, clearly, higher the K_{a} value , lower will the the pK_{a}

In this mixture, at equilibrium, [H^{+}] will be constant.

K_{a} of HF is grater than K_{a} of HCN

Hence, (\frac{F^{-}}{[HF]}=\frac{K_{a}(HF)}{[H^{+}]})>(\frac{CN^{-}}{[HCN]}=\frac{K_{a}(HCN)}{[H^{+}]})

So, \frac{[F^{-}]}{[HF]} is larger

8 0
4 years ago
Atom can<br> The ground state electronic configuration of<br> be represented by
Elan Coil [88]

Answer:

Ground state electronic configuration of nitrogen atom can be represented by 1, 4 only. All the unpaired electrons have spins aligned in the same direction only.

Explanation:

7 0
3 years ago
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