# Recently Submitted Homework Problems: chemistry

290. Find moles CO produced from 7 molesSio2 and 140g Ca(PO4)2(Answered)

775. what is noble gas configuration?(Answered)

1275. I have been assigned two different HC2H3O2 solution concentrations and two different Na2CO3 solution concentrations by my teacher. Acetic Acid: 0.0800M and 0.160M Carbonate Ion: 0.100M and 0.140M Determine the volume, in mL, of 2.00M HC2H3O2 required to prepare each and the mass of sodium carbonate to prepare each.

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1413. how do I round atomic masses when I do chemsitry calculations for example how would I round the atomic mass of helium in the problem:calcualate the mass of 5.22 mol of helium(Answered)

1439. If 17.5 mL of 0.50 N HCl are needed to titrate 35.0 mL of NaOH to the endpoint, what is the % concentration of the NaOH in the sample?(Answered)

1523. balancing chemical equations:

Pb(No3)2-->Pbo+No2+O2

(Answered)

1725. How do you calculate the mass of 1.58 moles of CH4?(Answered)

1726. what volume will 7.29 moles of CO2 gas occury at STP(Answered)

1912. the denstiy of iron is 7.86 g/cm3. you are given an unknown metal that has a volume of 30.1 cm3. what would the mass of the sample be if the metal is iron?(Answered)

2292. How many grams of calcium flouride are in 800mL of a 0.62 M calcium flouride solution?(Answered)

3310. To a 250 mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO3, 0.100 M NaBr, and 0.100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigorously. What mass of AgBr would precipitate from this mixture? [Hint: Ksp of AgBr=5.4*10^-13 and Kf of Ag(CN)2 ^- 1.0*10^21](Answered)

3425. A large weather balloon requires plenty of helium gas in order to ascend into the atmosphere to take measurements. If the balloon has a volume of 100,000 liters, about how many kilograms of helium gas would be required to fill the balloon to a pressure of 1 atm and a temperature of 27 degrees C?(Answered)

3752. The ratio R of radioactive carbon to nonradioactive carbon left in a sample of an organism that died T years ago can be approximated by the formula R=A(2.7)-T/8033. Here A is the ratio of radioactive carbon to nonradioactive carbon in the living organism. What percent of A is left after 2000 years? After 4000 years? After 8000 years?(Answered)

4378. help me solve this chemistry problem: fill in the blanks with numbers: Each NO molecule reacts with 1 O atom to produce 1 NO2 molecule. Therefore, ___ NO molecules react with ___ O atoms, which is equivalent to ___ O2 molecules, to form ___ NO2 molecules.

(Answered)

4499. the molecules in crude oil are?

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4521. Isopropyl alcohol has a melting point of 185.2 K, a boiling point of 355.4 K, a heat of fusion of 90.02 J/g, a heat of vaporization of 633.06 J/g, and the following specific heat values: the solid form has a specific heat of 0.003527 J/g K, liquid has a specific heat of 2.682 J/g K, and a gas has a specific heat of 1.715 J/g K. Determine how many joules of energy/heat are needed to warm 120.0 g of isopropyl alcohol from -100 Â°C to 100 Â°C. Draw out and label your heating curve.(Answered)

4700. SAVERDEVITE, A HIGHLY VOLATILE AND UNSTABLE SUBSTABLE, HAS A HALF-LIFE OF 2 YRS. IT DECAYS TO THE STABLE AND VALUABLE SUBTANCE TAYLORIUM. IN 1994 A 200 LB BLOCK OF PURE SAVERDEVITE WAS FOUND.

a) in what year will the block contain only 40 lbs of saverdevite?

b) in what year will it contain only 5 lbs of saverdevite?(Answered)

4700. SAVERDEVITE, A HIGHLY VOLATILE AND UNSTABLE SUBSTABLE, HAS A HALF-LIFE OF 2 YRS. IT DECAYS TO THE STABLE AND VALUABLE SUBTANCE TAYLORIUM. IN 1994 A 200 LB BLOCK OF PURE SAVERDEVITE WAS FOUND.

a) in what year will the block contain only 40 lbs of saverdevite?

b) in what year will it contain only 5 lbs of saverdevite?(Answered)

5128. A 2.56 g sample of anthracene, C14H10, was burned to heat an aluminum calorimeter (mass = 948 g). The calorimeter contained 1.50 L of water with an initial temperature of 20.5°C and a final temperature of 34.3°C.

Write the thermochemical equation, two ways, for the complete combustion of anthracene.

(Answered)

5138. the mole fraction of o2 in a co/o2 mixture is 0.4 what is the mole fraction of o2 after these gases react according to the following reaction?

2co + o2 > 2co2(Answered)