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. What is the mass, in grams, of a sample of 7.83 × 1024 atoms of helium (He)?

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. What is the mass, in grams, of a sample of 7.83 × 1024 atoms of helium (He)?

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Janitor supply produces an industrial cleaning powder that requires 40 grams of material at $0.10 per gram and .25 direct labor hours at $12.00 per hour. overhead is assigned at the rate of $18 per direct labor hour. what is the total standard cost for one unit of product that would appear on a standard cost card? $7.00. $8.50. $11.50. $7.50. $25.00.

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Janitor supply produces an industrial cleaning powder that requires 40 grams of material at $0.10 per gram and .25 direct labor hours at $12.00 per hour. overhead is assigned at the rate of $18 per direct labor hour. what is the total standard cost for one unit of product that would appear on a standard cost card? $7.00. $8.50. $11.50. $7.50. $25.00.

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How many grams of solute are present in 625 mL of 0.520 M KBr?

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How many grams of solute are present in 625 mL of 0.520 M KBr?

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If 63.8 grams of aluminum metal (Al) react with 72.3 grams of sulfur (S) in a synthesis reaction, how many grams of the excess reactant will be left over when the reaction is complete? Be sure to write out the balanced equation for this reaction and to show all of your work.

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The balanced chemical reaction would be:

16Al + 3S8 = 8Al2S3

We need to determine which reactants are the limiting and the excess. To determine this, we use the initial amounts of the reactants given above. We need to convert them into units of moles and use the balanced reaction to relate the substances calculating the amount needed to react all of the reactants. We do as follows:

63.8 g Al ( 1 mol Al / 26.98 g Al ) ( 3 mol S8 / 16 mol Al ) (256.48 g S / 1 mol S )= 113.72 g S8 needed to completely react
72.3 g S8 ( 1 mol S8 / 256.48 g S8) ( 16 mol Al / 3 mol S8 ) ( 26.98 g / mol ) = 40.56 g Al needed to completely react

Therefore, the excess would be Al and the limiting would be sulfur. The amount excess would be 63.8 g Al  – 40.56 g Al = 23.24 g Al

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How many grams are there in 2.3 x 10^24 atoms of silver?

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How many grams are there in 2.3 x 10^24 atoms of silver?

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What is the density of a block of aluminum that has mass 27 grams of and a volume 10 cm3? 2.7 g/cm3 270 g/cm3 0.37 g/cm3 0.37 cm3/g

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What is the density of a block of aluminum that has mass 27 grams of and a volume 10 cm3? 2.7 g/cm3 270 g/cm3 0.37 g/cm3 0.37 cm3/g

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Margo boils 500mL of water to make 80 g of pasta. If Margo boils 2500mL of water, how many grams of pasta can she make?

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Margo boils 500mL of water to make 80 g of pasta. If Margo boils 2500mL of water, how many grams of pasta can she make?

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If 0.9 grams of calcium burnt in air the weight of product formed is?

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If 0.9 grams of calcium burnt in air the weight of product formed is?

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How many moles of oxygen are in 52.5 grams of oxygen gas?

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An oxygen gas is a diatomic molecule which means that each molecule is composed of 2 atoms. Its symbol is O2. 

Each oxygen atom has a molar mass of 16 g/mol. The molar mass of oxygen gas is calculated below,
                         molar mass = 2 x (16 g/mol) = 32 g/mol

To determine the number of moles in 52.5 grams of oxygen, divide the given mass by the calculated molar mass.
 
                                 n = 52.5 grams / (32 gram/ mol)
                                     n = 1.64 moles

Thus, there are 1.64 moles of oxygen gas. 

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The brain mass of a fetus can be estimated using the total mass of the fetus by the function b equals 0.22 m superscript 0.87b=0.22m0.87?, where m is the mass of the fetus? (in grams) and b is the brain mass? (in grams). suppose the brain mass of a 2323?-g fetus is changing at a rate of 0.240.24 g per day. use this to estimate the rate of change of the total mass of the? fetus, startfraction dm over dt endfraction dm dt.

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We are given
b = 0.22 m^0.87
db/dt = 0.24 g/day at b = 23 g

where
b is the brain mass of the fetus
m is the total mass of the fetus
db/dt is the rate of change of the brain mass of the fetus

We are asked to get the rate of change of the total mass of the fetus

First, we take the first derivative of the given equation with respect to time
db/dt = 0.22 (0.87) m^(0.87-1) dm/dt
Next, simplify and substitute the given values. So,
0.24 g/day = 0.22(0.87)(23)^(0.87 -1 ) dm/dt
Solving for dm/dt
dm/dt = 1.88 g/day

The rate of change of mass of the fetus is 1.88 g/day.

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White gold is an alloy that typically contains 45.0% by mass gold and the remainder is platinum. if 154 g of gold are available, how many grams of platinum are required to combine with the gold to form this alloy?

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Percent by mass of platinum in white gold = 100% – 45% = 55%

We let x be the mass of the white which is 45% gold and 55% platinum. 

Mass of gold in white gold = m x 0.45

where m is the total mass.

From the given above, we formulate the equation that would allow us to determine the mass of white gold.
                            154 = x (0.45)
                                     x = 342.22 g

Then, we determine the amount of platinum.
                     mass of platinum = (342.22 g)(0.55)
                      mass of platinum = 188.22 grams

Thus, 188.22 grams of platinum is needed. 

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If 1 g of hydrogen combines completely with 8 g of oxygen to form water, how many grams of hydrogen does it take to combine completely with 64 g of oxygen?

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The balanced chemical reaction would be:

2H2 + O2 = 2H2O

We are given the amount of oxygen to react with hydrogen. To determine the amount of hydrogen needed for the oxygen to completely react, we use the balanced reaction to relate the substances. We do as follows:

64 g O2 ( 1 mol / 32 g ) ( 2 mol H2 / 1 mol O2 ) ( 2.02 g / 1 mol ) = 8.08 g of hydrogen gas needed

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An unknown, rectangular substance measures 3.6 cm high, 4.21 cm long, and 1.17 cm wide. if the mass is 21.3 g, what is this substances density (in grams per milliliter)?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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How many grams of glucose are needed to prepare 400 ml of a 2.0% glucose solution?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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A sample of gold has a mass of 38.6 grams and a volume of 2 cm3. What is the density of gold?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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Mass of empty 10 mL graduated cylinder (grams)

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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You have a 1 kilogram bag of sugar. You use 435 grams to fill the sugar bowls. How much sugar is left in the bag?answer in grams

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Answer:

The age of a rock is determined by the function:

A(t) = A_0 cdot e^{-0.000002t}             …..[1]

where,

A(t) be the age of rock after t years

A_0 be the initial value of Isotope Q.

t be the number of years.

As per the statement:

A sample originally has 80 grams of Isotope Q, decays, and now has 20 grams of the isotope.

A_0 = 80 gram and A(t) = 20 grams

Substitute in [1] we have;

20 =80 cdot e^{-0.000002t}

Divide both sides by 80 we have;

0.25 = e^{0.000002t}

Taking ln with base e both sides we have;

ln 0.25 = -0.000002t

-1.3862943611199 = -0.000002t

Divide both sides by 0.000002 we have;

693147.18056  = t

or

t = 693147.18056  years

Therefore, the current age of the sample, in years to the nearest thousand years is, 6,93,147 year

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Combustion analysis of an unknown compound provides the following data: 73.5 grams carbon (C), 4.20 grams hydrogen (H) and 72.3 grams chlorine (Cl). What is the percent composition of each element in this compound?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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If the mass of one mole of hydrogen is 1.01 grams; phosphorus, 30.97 grams; and oxygen, 16.0 grams, what is the molar mass of phosphoric acid (H3PO4)?

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The balanced chemical reaction is as shown below,

                 N₂ + 3H₂  –> 2NH₃

The equation shows that every 3 moles of hydrogen, H2, there would be 2 moles of ammonia, NH3, that is going to be formed. Using this concept, we solve for the unknown in this item. 

Since we are restricted only of the number of hydrogen, it becomes our limiting reactant. 

          (6 moles H2) x (2 moles NH3/3 moles H2) = 4 moles NH3

Therefore, given enough amount of N2, the amount of NH3 that can be formed out of the 6 moles of H2 is equal to 4 moles. 

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How many milliliters of sodium metal, with a density of 0.97 g/mL, would be needed to produce 34.5 grams of sodium hydroxide in the single replacement reaction below? Unbalanced equation: Na + H2O —> NaOH + H2

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The balanced chemical reaction is as shown below,

                 N₂ + 3H₂  –> 2NH₃

The equation shows that every 3 moles of hydrogen, H2, there would be 2 moles of ammonia, NH3, that is going to be formed. Using this concept, we solve for the unknown in this item. 

Since we are restricted only of the number of hydrogen, it becomes our limiting reactant. 

          (6 moles H2) x (2 moles NH3/3 moles H2) = 4 moles NH3

Therefore, given enough amount of N2, the amount of NH3 that can be formed out of the 6 moles of H2 is equal to 4 moles. 

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Iodine-123 is a radioactive substance used in medicine. It has a half-life of 13 hours. A nurse received a solution that initially contained 48 grams of iodine-123. Now only 12 grams of the iodine-123 remain. How many hours have passed since the nurse received the solution?

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Answer:

                The point that lie on the line is:

                        B.  (1,1)

Step-by-step explanation:

We are given that a line passes through the point (0,-1) and has a slope of 2.

We know that the equation of a line passing through (a,b) and having slope m is given by:

           y-b=m(x-a)

Here we have:  (a,b)=(0,-1) and m=2

This means that the equation of line is:

y-(-1)=2(x-0)\\y+1=2x\\y=2x-1

Now we will check which option is true.

A)

                (2,1)

when x=2

we have:

y=2times 2-1\\\y=4-1\\\y=3neq 1

Hence, option: A is incorrect.

B)

                     (1,1)

when x=1

we have:

y=2times 1-1\\\y=2-1\\\y=1

                Hence, option: B is correct.

C)

                      (0,1)

when x=0

we have:

y=2times 0-1\\\y=0-1\\\y=-1neq 1

Hence, option: C is incorrect.

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When 13.6 grams of kcl are dissolved in enough water to create a 180-gram solution, what is the solution’s concentration, expressed as a percent by mass? 4.6% kcl 6.8% kcl 7.6% kcl 8.2% kcl?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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Suppose you dissolved 0.123 gram of pentane in 2.493 grams of p-xylene and measured a freezing point depression of 2.88 degrees celcius for the solution. Calculate the molar mass of pentane using this data and the value for Kf that you calculated in question 1 I got .829 mol/kg for question 1

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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How many grams of hydrochloric acid will react completely with a block of gold that is 3.2 cm by 3.8 cm by 2.8 cm, if the density of gold is 19.3 g/ml?

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This problem is to apply Roult’s Law.

Roult’s Law states that the vapor pressure, p, of a solution of a non-volatile solute is equal to the vapor pressure of the pure solvent, Po solv, times the mole fraction of the solvent, Xsolv

p = Xsolv * Po sol

X solv = number of moles of solvent / number of moles of solution

The solvent is water and the solute (not volatile) is glycerin.

Number of moles = mass in grams / molar mass

mass of water = 132 ml * 1 g/ml = 132 g

molar mass of water = 18 g/mol

=> number of moles of water = 132 g / 18 g/mol = 7.33333 mol

mass of glycerin = 27.2 g

molar mass of glycerin:, C3H8O3: 3 * 12 g/mol + 8 * 1 g/mol + 3*16 g/mol = 92 g/mol

number of moles of glycerin = 27.2g / 92 g/mol = 0.29565

total number of moles = 7.33333 moles + 0.29565 moles = 7.62898 moles

=> X solv = 7.33333 / 7.62898 = 0.96125

=> p = 0.96125 * 31.8 torr ≈ 30.57 torr ≈ 30.6 torr.

Answer: 30.6 torr

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The theoretical yield for a reaction is 80 grams. The reaction ends up having a percent yield of 40%. How many grams were actually produced in the reaction? 3.2 g 32 g 50 g 80 g

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Answer:

The coefficient of CO₂ is 5.

Explanation:

    Balancing the reaction:

___C₅H₁₂ + ___O₂ → ___CO₂ + ___H₂O

There are 5 C in the left side, so we put 5 on the right side:

___C₅H₁₂ + ___O₂ →  5CO₂ + ___H₂O

There are 12 H in the left side, so we put 6 as the coefficient of H₂O:

___C₅H₁₂ + ___O₂ →  5CO₂ + 6H₂O

Finally, there are 16 O in the right side, so we put 8 as the coefficient of O₂

___C₅H₁₂ + 8O₂ →  5CO₂ + 6H₂O

The coefficient of CO₂ is 5.

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