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Contact [7]
3 years ago
10

How is enthalpy used to predict whether a reaction is endothermic or exothermic?

Chemistry
1 answer:
Black_prince [1.1K]3 years ago
8 0
When the enthalpy change of the reaction is positive, the reaction is exothermic. 
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How many ml of a .4 % solution of nalorphine must be injected to obtain a dose of 1.5 mg
wolverine [178]

0.4% = 0.004

(1.5mg /1000g ) / 0.004 = 0.375ml

4 0
3 years ago
Nguyên tố X có hai đồng vị, đồng vị thứ nhất có số khối 35 chiếm 75%. Nguyên tử khối trung bình của X là 35,5. Đồng vị thứ hai c
BlackZzzverrR [31]

Answer:

C

Explanation:

  • Why (C) because it is the correct answer
  • about my answer i how it correct
4 0
3 years ago
What is the molarity of a salt solution made by dissolving 250.0 grams of NaCl in 775 mL of solution?
tester [92]

The molarity of a salt solution made by dissolving 250.0 grams of NaCl in 775 mL of solution is <u>5.52 M</u> .

<u>Explanation:</u>

The molarity of a solution tells one how many moles of <u>solute</u> one can get <em>per liter</em> of solution.One should remember to must convert this volume to liters by using the conversion factor:

1 L = 10³ml

Sodium chloride (NaCl) has a molar mass of 58.44 g per mol , which means that the sample will contain:

   250 \mathrm{g} \times \frac{1 \text { mole of } \mathrm{Nacl}}{58.44 \mathrm{g}}=4.278 \text { mole of } \mathrm{Nacl}

This means that the molarity of the solution will be:

\text {Molarity,c}=\frac{n_{\text {solute}}}{V_{\text {solution }}}=\frac{4.28}{775 \times 10^{-3}}=0.00552 \times 10^{3}=5.52 M

7 0
3 years ago
A hot-air balloon is filled with air to a volume of 3000 m3 at 750 torr and 21°C. The air in the balloon is then heated to 60.°C
valina [46]

Answer: 1.47

Explanation:

The combined gas equation when pressure is constant:

\frac{V_1}{n_1T_1}=\frac{V_2}{n_2T_2}

where,

n_1 =original number of moles of air in the balloon = ?

n_2 =  number of moles of air in the heated balloon = ?

V_1 = initial volume of gas = 3000m^3

V_2 = final volume of gas = 5000m^3

T_1 = initial temperature of gas = 21^oC=273+21=294K

T_2 = final temperature of gas = 60^oC=273+60=333K

Now put all the given values in the above equation, we get the final pressure of gas.

\frac{3000}{n_1\times 294K}=\frac{5000}{n_2\times 333K}

\frac{n_2}{n_1}=1.47

Therefore, the  ratio of the number of moles of air in the heated balloon to the original number of moles of air in the balloon is 1.47

5 0
3 years ago
What is a molecule containing only carbon and hydrogen called?
pogonyaev

Answer:

d

Explanation:

it's called the hydrocarbon

4 0
4 years ago
Read 2 more answers
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