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dlinn [17]
3 years ago
11

SCIENCE!!!! PLEASE HELP!!! 20 POINTS

Chemistry
2 answers:
Annette [7]3 years ago
4 0

Answer:

As the Earth rotates, it also moves, or revolves, around the Sun. ... As the Earth orbits the Sun, the Moon orbits the Earth. The Moon's orbit lasts 27 1/2 days, but because the Earth keeps moving, it takes the Moon two extra days, 29 1/2, to come back to the same place in our sky.

Explanation:

sertanlavr [38]3 years ago
3 0
The answer above I believe is correct I was gonna say the same!!! GG
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A block of magnesium has a mass of 14.3 g and a volume of 8.46 cm3. What is the density of
sveta [45]
Density is mass over volume, so:
14.3/8.46≈ 1.6903 g/cm^3
7 0
2 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,
bonufazy [111]

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

5 0
3 years ago
Your body is much larger now than it was when you were a baby. What is the cause of this growth? *
masya89 [10]

Answer:c

Explanation:

4 0
3 years ago
Read 2 more answers
How many atoms are in a sample of chromium with a mass of 31 grams? O a 2.4 x 1024 atoms of chromium b 3.6 x 1023 atoms of chrom
lukranit [14]

Answer:

b. 3.66x10²³ atoms of chromium.

Explanation:

First we calculate how many moles are there in 31 grams of chromium, using its molar mass:

  • Molar Mass of Chromium = 51 g/mol (This can be found on any periodic table)
  • 31 g ÷ 51 g/mol =  0.608 mol

Then we <u>calculate how many atoms are there in 0.608 moles</u>, using <em>Avogadro's number</em>:

  • 0.608 mol * 6.023x10²³ atoms/mol = 3.66x10²³ atoms

The correct answer is thus option b. 3.66x10²³ atoms of chromium.

4 0
3 years ago
A 256 mL sample of HCl gas is in a flask where it exerts a force (pressure) of 67.5 mmHg. What is the pressure of the gas if it
Effectus [21]

Answer:

The pressure in the new flask would be 128\; \rm mmHg if the \rm HCl here acts like an ideal gas.  

Explanation:

Assume that the \rm HCl sample here acts like an ideal gas. By Boyle's Law, the pressure P of the gas should be inversely proportional to its volume V.

For example, let the initial volume and pressure of the sample be V_1 and P_1. The new volume V_2 and pressure P_2 of this sample shall satisfy the equation: P_1 \cdot V_1 =P_2 \cdot V_2.

In this question,

  • The initial volume of the gas is V_1= 256\; \rm mL.
  • The initial pressure of the gas is P_1 = 67.5\; \rm mmHg.
  • The new volume of the gas is V_2 = 135\; \rm mL.

The goal is to find the new pressure of this gas, P_2.

Assume that this sample is indeed an ideal gas. Then the equation P_1 \cdot V_1 =P_2 \cdot V_2 should still hold. Rearrange the equation to separate the unknown, P_2. Note: make sure that the units for V_1 and V_2 are the same before evaluating. That way, the unit of

\begin{aligned} & P_2\\ &= \frac{P_1 \cdot V_1}{V_2} \\ &= \frac{256\; \rm mL \times 67.5\; \rm mmHg}{135\; \rm mL} \\ & \approx 128\; \rm mmHg\end{aligned}.

3 0
3 years ago
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