Hydrogen cyanide, HCN, is a poisonous gas. The lethal dose...

Hydrogen cyanide, HCN, is a poisonous gas. The lethal dose is approximately 320 mg HCN per kilogram of air when inhaled. Part A Calculate the amount of HCN that gives the lethal dose in a small laboratory room measuring 14 x 15 x 8.0ft. The density of air at 26° C is 0.00118g/cm^3. Express your answer using two significant figures. m = 18 g Part B If the HCN is formed by reaction of NaCN with an acid such as H2SO4, what mass of NaCN gives the lethal dose in the room? 2NaCN(s) + H2SO4(aq) -> Na2SO4(aq) + 2HCN(g) Express your answer using two significant figures. m = [ ] g

Transcript

00:01 Lethal dose of hydrogen cyanide.

00:02 So we know that the lethal dose is 320 milligrams per kg of air.

00:21 So this is a lethal dose.

00:22 So now you have a room that is 14 times 15 times 8 feet, and you know the density.

00:33 The question asks you to calculate the amount of hcn that gives the the lethal dose.

00:38 So first of all, you want to calculate the volume of the room.

00:43 So the volume of the room equals width times length times height.

00:52 First of all, you can see that the density of the air has 0 .00118 gram per cubic centimeter, and then you have the room in a unit of feet so you will have to convert the foot to cm first.

01:07 Since 1 inch equals 2 .54 centimeter and 1 foot is 12 inches so we know that 1 foot equals about 30 .48 centimeter.

01:23 So now let's do our math.

01:26 The room is 14 feet feet times 30 .48 centimeters times 15 times 30 .48 times 8 times 30 .48.

01:50 And then that's in a unit of cubic centimeters.

01:53 And that equals equals 4757202, let's say, cubic centimeter.

02:08 I round it up to the nearest one.

02:10 Now, we know that the density of air at 26 degrees celsius is 0 .0011 agram per cubic centimeter.

02:22 So we want to calculate the mass of air.

02:33 So density multiplied by volume, so basically 0 .00118 gram per cubic centimeter times 4757202 cubic centimeter.

03:01 And then you can cancel that out.

03:03 And you end up having 50 ,135 grams of air.

03:15 And then you know that the lethal dose is in the per kg.

03:19 So this is g.

03:21 So to convert into kg, 1g equals 10 to the negative 3 kg.

03:28 So then 56 ,135 grams gram multiplied by 10 to the negative 3 is 56 .1 kg.

03:41 So let's just leave it as one decimal, because the question asks you to express the answer with two significant figures.

03:53 All right, so now the next step, you want to calculate the amount of hcn, the hydrogen cyanide.

04:05 We know that the diesel dose is 320 mg per kg of air...

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