The actual enthalpy of the magnesium flare reaction is –603 kj/mol. your experimental value was likely different. check all that apply.

the coffee cup calorimeter may have absorbed some heat.

the plastic coffee cup lid may have allowed some heat to escape.

the thermometer did not measure the temperature of the solution properly.

reading the maximum temperature values from the thermometer could be challenging.

a,b,d

Explanation:

1st part: A, B, D

2nd part: 8.62%

Explanation:

linda: 3 ; laura: 15

step-by-step explanation:

note that linda + laura's age is 18, and that linda is 12 years younger than her sister.

let "linda" = x , "laura" = y:

x + y = 18

x = y - 12

first, plug in y - 12 for x in the first equation:

(y - 12) + y = 18

simplify.

2y - 12 = 18

isolate the variable (y). note the equal sign, what you do to one side, you do to the other. do the opposite of pemdas. first add, then divide.

2y - 12 (+12) = 18 (+12)

2y = 18 + 12

2y = 30

(2y)/2 = (30)/2

y = 30/2

y = 15

next, plug in 15 for y in the second equation (the other equation would work too).

x = y - 12

x = (15) - 12

x = 3

linda's age is 3, laura's age is 15.

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