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Lady_Fox [76]
3 years ago
14

Calculate 18.9 minus 2.15. Round the answer to the correct number of significant figures.

Chemistry
1 answer:
Lerok [7]3 years ago
7 0
The answer is 16.75 it rounds to 17 Hope this helps! ;D
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A chemist must prepare 300.0mL of nitric acid solution with a pH of 0.70 at 25°C. He will do this in three steps: Fill a 300.0mL
d1i1m1o1n [39]

<u>Answer:</u> The volume of concentrated solution required is 9.95 mL

<u>Explanation:</u>

To calculate the pH of the solution, we use the equation:

pH=-\log[H^+]

We are given:

pH = 0.70

Putting values in above equation, we get:

0.70=-\log[H^+]

[H^+]=10^{-0.70}=0.199M

1 mole of nitric acid produces 1 mole of hydrogen ions and 1 mole of nitrate ions.

Molarity of nitric acid = 0.199 M

To calculate the volume of the concentrated solution, we use the equation:

M_1V_1=M_2V_2

where,

M_1\text{ and }V_1 are the molarity and volume of the concentrated nitric acid solution

M_2\text{ and }V_2 are the molarity and volume of diluted nitric acid solution

We are given:

M_1=7.0M\\V_1=?mL\\M_2=0.199M\\V_2=350mL

Putting values in above equation, we get:

7.0\times V_1=0.199\times 350.0\\\\V_1=\frac{0.199\times 350}{7.0}=9.95mL

Hence, the volume of concentrated solution required is 9.95 mL

6 0
2 years ago
The specific heat of copper is 0.40 joules/ g °c. How much heat is needed in joules to change the temperature of a 55 gram subst
Snezhnost [94]

Answer : The amount of heat needed is, 1188 J

Explanation :

Formula used :

q=m\times c\times (T_2-T_1)

where,

q = heat needed = ?

m = mass of copper = 55 g

c = specific heat capacity of copper = 0.40J/g^oC

T_1 = initial temperature = 20.0^oC

T_2 = final temperature = 74.0^oC

Now put all the given values in the above formula, we get:

q=55g\times 0.40J/g^oC\times (74.0-20.0)^oC

q=1188J

Thus, the amount of heat needed is, 1188 J

3 0
3 years ago
When three pairs of electrons are shared in a molecule, what shape will the molecule be?
djyliett [7]
The correct answer is B. The shape of a molecule where three pairs of electrons are shared is a trigonal planar. This is characterized by one central atom and three atoms forming an equilateral triangle which is bonded to the central atom.
8 0
2 years ago
Read 2 more answers
To balance a chemical equation, it may be necessary to adjust the
lana66690 [7]

Answer:

A. Coefficients

Explanation:

that's the number in front of the molecules

7 0
3 years ago
What volume of a 0.100 M AgNO3 solution is required to completely react with the CaCl2 in 3.00 L of a 0.100 M CaCl2 solution? Th
Andreyy89

Answer:

6.00 LAgNO3

Explanation:

Got it right on Edge. :)

5 0
3 years ago
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