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Marina86 [1]
3 years ago
9

I have a exam please answer fast

Chemistry
1 answer:
VLD [36.1K]3 years ago
3 0

Answer:

C

\triangle \: H {}^{ \theta}  _{s} = lattice \: energy + hydration \: energy \\  =   + 2526 + ( - 2003 + (2 \times  - 340)) \\  + 2526 - 2683 \\  =  - 157 \: kjmol {}^{ - 1}

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Eyeglasses provide as much protection as safety goggles. * true or false
Artyom0805 [142]
False. Eyeglasses do not cover all around the eye however safety goggles do
7 0
3 years ago
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We dissolve 93 grams of sodium sulfate (Na2SO4) in 20 grams of water. What is the percent by mass of sodium sulfate in this solu
dlinn [17]
It should be for the total solution of 93 plus 20 grams which is 113 grams so 93 divided by 113 grams comes to 82.3% sodium sulfate and this can be checked by multiplying 113 grams by 0.823 which results in 93 grams of sodium sulphate. 
4 0
3 years ago
What is the volume of 1.50 lb (pounds) of mercury? The density of mercury is 13.546 g/mL. Use the conversion that 1 kg = 2.20 lb
Arada [10]

Answer:

50.3mL of mercury are in 1.50lb

Explanation:

Punds are an unit of mass. To convert mass to volume we must use density (13.546g/mL). Now, As you can see, density is in grams but the mass of mercury is in pounds. That means we need first, to convert pounds to grams to use density and obtain volume of mercury.

<em>Mass mercury in grams:</em>

1.50lb * (1kg / 2.20lb) = 0.682kg = 682g of mercury.

<em>Volume of mercury:</em>

682g Mercury * (1mL / 13.546g) =

<h3>50.3mL of mercury are in 1.50lb</h3>
7 0
3 years ago
Question 1 of 15<br> 2 Points<br> What is another name for a pure substance?<br> Answer here
maksim [4K]

Answer:

element

Explanation:

elements consist of pure substances

4 0
3 years ago
1. An electric power plant uses energy from burning coal to generate steam at 450 °C. The plant is cooled by 20 °C water
kap26 [50]

Answer:

Explanation:

Efficiency of the electric power plant is e=1-\frac{T_{2}}{T_{1}}

Here Temperature of hot source T_{1} = 450^{o}C=450+273=723 K

and Temperature of sink T_{1} = 20^{o}C=20+273=293 K

Hence the efficiency is  e=1-\frac{293}{723}=0.5947=59.47%

Now another formula for thermal efficiency Is

e_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}

Here QI is the of heat taken from source 100 MJ ; Q2 of heat transferred to the sink (river) to be found

W is the of work done and W = QI -Q2

Hence Frome_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}

W=e(Q_{1})=(0.5947)(100)=59.47MJ

Hence the of heat transferred to the river Is Q_{2} -W = (100 -59.47=40.53

6 0
3 years ago
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