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3 years ago

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:

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 5.52 M .

Explanation:

The molarity of a solution tells one how many moles of solute one can get per liter 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:

Explanation:

it's called the hydrocarbon

4 0

4 years ago

Read 2 more answers