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3 years ago

If the mass of a cube with a length of 9.0 cm3 is 12.2 g what is its density

Chemistry

2 answers:

Anvisha [2.4K]3 years ago

7 0

Answer:

The density is 1,35 g/cm3

Explanation:

We use the formula for calculate the density

δ =m/V =12,2g / 9,0 cm3= 1,35 g/cm3

arsen [322]3 years ago

6 0

Answer:

Check for a possible typo in your text, and pick the answer appropriately as explained below:

The cube's density is either $1.356\frac{g}{cm^3}$ , or $0.0167\frac{g}{cm^3}$

Explanation:

There is something incoherent with the dimensions shown in the question: The length of an abject cannot be given in cubic centimeter. It could be just centimeter (cm). Now, if you typed "length" by error, and the word in the question was in fact "volume", the units would be correct.

I am writing below the answers for either case, but please check what the correct enunciation of the problem was:

A) In the case in which the problem stated: If the mass of a cube with a length of 9.0 cm is 12.2 g, what is its density?

The steps are: 1) Recall that the formula for density states that it is the mass of the object divided its volume. The mass is given to you, but only the length of a side of the cube is the info, so you need to find the cube's volume by multiplying 9cm * 9cm *9cm = 729 $cm^3$ Thus, the density is calculated as the quotient: $Density=\frac{mass}{volume} =\frac{12.2}{729} \frac{g}{cm^3} = 0.0167\frac{g}{cm^3}$

B) In the case the info shown is a volume and not a length, then you don't need to evaluate the volume of the cube (it is already given to you as 9 $cm^3$ ), and you use it directly in the equation:

$Density=\frac{mass}{volume} =\frac{12.2}{9} \frac{g}{cm^3} = 1.356\frac{g}{cm^3}$

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45 Three samples of the same solution are tested, each with a different indicator. All three indicators, bromthymol blue, bromcr

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Answer: The correct answer is Option 4.

Explanation:

Bromothymol blue, Bromocresol green and Thymol blue are the indicators which change their color according to the change in pH of the solution.

The pH range and color change of these indicators are:

Bromothymol Blue: The pH range for this indicator is 6.0 to 7.5 and color change is from yellow to blue. It appears yellow below pH 6.0 and blue above pH 7.5
Bromocresol green: The pH range for this indicator is 3.5 to 6.0 and color change is from yellow to blue. It appears yellow below pH 3.5 and blue above pH 6.0
Thymol Blue: The pH range for this indicator is 8.0 to 9.6 and color change is from yellow to blue. It appears yellow below pH 8.0 and blue above pH 9.6

As, the highest pH of all the indicators is 9.6, so every indicator will appear blue above pH 9.6.

Hence, the correct answer is Option 4.

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3 years ago

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Hard water often contains dissolved Ca2+ and Mg2+ ions. One way to soften water is to add phosphates. The phosphate ion forms in

avanturin [10]

5.5×10−2M in calcium chloride and 8.0×10−2M in magnesium nitrate.
What mass of sodium phosphate must be added to 1.5L of this solution to completely eliminate the hard water ion

1) Content of Ca (2+) ions

Calcium chloride = CaCl2

Ionization equation: CaCl2 ---> Ca (2+) + 2 Cl (-)

=> Molar ratios: 1 mol of CaCl2 : 1 mol Ca(2+) : 2 mol Cl(-)

Calculate the number of moles of CaCl2 in 1.5 liters of 5.5 * 10^-2 M solution

M = n / V => n = M*V = 5.5 * 10^ -2 M * 1.5 l = 0.0825 mol CaCl2

=> 0.0825 mol Ca(2+)

2) Number of phosphate ions needed to react with 0.0825 mol Ca(2+)

formula of phospahte ion: PO4 (3-)

molar ratio: 2PO4(3-) + 3Ca(2+) = Ca3 (PO4)2

Proportion: 2 mol PO4(3-) / 3 mol Ca(2+) = x / 0.0825 mol Ca(2+)

=> x = 0.0825 coml Ca(2+) * 2 mol PO4(3-) / 3 mol Ca(2+) = 0.055 mol PO4(3-)

3) Content of Mg(2+) ions

Ionization equation: Mg (NO3)2 ----> Mg(2+) + 2 NO3 (-)

Molar ratios: 1 mol Mg(NO3)2 : 1 mol Mg(2+) + 2 mol NO3(-)

number of moles of Mg(NO3)2 in 1.5 liter of 8.0 * 10^-2 M solution

n = M * V = 8.0 * 10^ -2 M * 1.5 liter = 0.12 moles Mg(NO3)2

ions of Mg(2+) = 0.12 mol Mg(NO3)2 * 1 mol Mg(2+) / mol Mg(NO3)2 = 0.12 mol Mg(2+)

4) Number of phosphate ions needed to react with 0.12 mol Mg(2+)

2PO4(3-) + 3Mg(2+) = Mg3(PO4)2

=> 2 mol PO4(3-) / 3 mol Mg(2+) = x / 0.12 mol Mg(2+)

=> x = 0.12 * 2/3 mol PO4(3-) = 0.16 mol PO4(3-)

5) Total number of moles of PO4(3-)

0.055 mol + 0.16 mol = 0.215 mol

6) Sodium phosphate

Sodium phosphate = Na3(PO4)

Na3PO4 ---> 3Na(+) + PO4(3-)

=> 1 mol Na3PO4 : 1 mol PO4(3-)

=> 0.215 mol PO4(3-) : 0.215 mol Na3PO4

mass in grams = number of moles * molar mass

molar mass of Na3 PO4 = 3*23 g/mol + 31 g/mol + 4*16 g/mol = 164 g/mol

=> mass in grams = 0.215 mol * 164 g/mol = 35.26 g

Answer: 35.26 g of sodium phosphate

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3 years ago

Which statement correctly identifies the nuclide that is most likely to be unstable and describes why?

iVinArrow [24]

The answer would be B.

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It is actually the most commonly used isotope is reactors.

C-14 is also a radioactive isotope with 8 neutrons and 6 protons.

The usual and ideal n to p ratio is 1:1 such as C-12 or Mg-24

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3 years ago

Which ingredients are needed to transform nadp to nadph?.

Ipatiy [6.2K]

Answer:

according to online:

"Hydrogen ions are transported with the electrons along the chain of reactions. In photosystem I, the electrons are energized, and the energy is stored in molecules of NADP+. During these reactions, the NADP+ molecules are reduced by the addition of electrons. A hydrogen ion is added to NADP+ to form NADPH."

Explanation:

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2 years ago

The mean radius of the Earth is 6,371 km, and 70.8% of its surface is covered by water. What is the surface area of the Earth co

Marina CMI [18]

Answer:

147,558,601 sqkm

Explanation:

The earth is spherical in shape;

area of sphere = 4πr²

if 70.8% is covered by water then 100-70.8 will be land,

= 29.2%

area occupied by land = (29.2/100) * 4πr²

= 0.292*4*3.142*(6371)²

=147,558,601 sqkm

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3 years ago