What is the sign of the heat change for an exothermic reaction? for an endothermic reaction?

1 answer:

3 0

A system that releases heat to the surroundings, an exothermic reaction, has a negative ΔH by convention, because the enthalpy of the products is lower than the enthalpy of the reactants of the system. The enthalpies of these reactions are less than zero, and are therefore exothermic reactions

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How many moles are contained in 2.3 liters of a 1.2M solution?

elena-s [515]

Answer:

$\boxed {\boxed {\sf 2.76 \ mol}}$

Explanation:

Molarity is found by dividing the moles of solute by liters of solution.

$molarity = \frac {moles}{liters}$

We know the molarity is 1.2 M (mol\liter) and there are 2.3 liters of solution. Substitute the known values into the formula.

$1.2 \ mol/liter= \frac {x}{2.3 \ liters}$

Since we are solving for x, we must isolate the variable. It is being divided by 2.3 and the inverse of division is multiplication. Multiply both sides by 2.3 liters.

$2.3 \ liters *1.2 \ mol/liter= \frac {x}{2.3 \ liters}* 2.3 \ liters\\2.3 *1.2 \ mol= x\\2.76 \ mol =x$

In a solution with a molarity of 1.2 and 2.3 liters of solution, there are 2.76 moles.

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A cylinder with a piston is full of gas which of the following actions would result in an increase in the pressure of the gas be

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The answer is B. Decreasing the cylinder volume decreases the amount of space the gas has to occupy there for increasing pressure

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The rate of acceleration of an object is determined by the mass of the object and...

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Answer:

a. forces acting on the object

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7. What happen if we don't have water?

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Answer:

our bodies will dehydrate causing us to die a dreadfully excruciating painful death

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The solubility of nacl at 30°c is 36.3 g/100 g of water. what mass of nacl is contained in a saturated solution that contains 30

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Because a solubility is calculated for saturated solutions we can write:

36.3 g NaCl ---100g water
x g NaCl ---- 300.0 g water

x=36.3*300/100=108.9 g NaCl

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