If a sealed syringe is plunged into cold water, in which direction will the syringe piston slide?

What is the cost in dollars for the nails used to build a fence 80 meters long if it requires 30 nails per meter? There are 40 n

svet-max [94.6K]

Answer:

4500 cent

Explanation:

From the question, we were told that

a fence 80 meters long requires 30 nails per meter.

1 metre fence = 30 nails

Then 80 meters long= ( 30 × 80)

= 2400 nails

Which means a fence 80 meters long will require 2400 nails in total.

We need to find the cost in dollars for the nails to build a fence 80 meters long.

We know that 40 nails per box will cost 75 cents per box.

(2400 nails/40 nail per box)= 60 box

Then 60 box will be needed to complete the fence.

the cost in dollars for the nails to build a fence 80 meters long= (60 box × 75 cent per box)=4500 cent

7 0

3 years ago

Why do scientists use the scientific method?

xeze [42]

Answer:

Scientists use the scientific method because it is evidence-based, standardized and objective in conducting experiments. The scientific method allows scientists to stick to facts and to avoid the influence of preconceived notions and personal biases in research processes, improving the credibility of research findings.

Explanation:

4 0

3 years ago

????????????????????????<br>thanks

sashaice [31]

D. I, II, and IV. Basically everything but the temperature.

6 0

4 years ago

Look at the following data provided below:

Vlad1618 [11]

Considering the Hess's Law, the enthalpy change for the reaction is -84.4 kJ.

Hess's Law indicates that the enthalpy change in a chemical reaction will be the same whether it occurs in a single stage or in several stages. That is, the sum of the ∆H of each stage of the reaction will give us a value equal to the ∆H of the reaction when it occurs in a single stage.

<h3>Enthalpy change for the reaction in this case</h3>

In this case you want to calculate the enthalpy change of:

2 C (graphite) + 3 H₂(g) → C₂H₆(g)

which occurs in three stages.

You know the following reactions, with their corresponding enthalpies:

Equation 1: C₂H₆(g) + $\frac{7}{2}$ O₂(g) → 2 CO₂(g) + 3 H₂O(l) ; ΔH° = –1560 kJ

Equation 2: H₂(g) + $\frac{1}{2}$ O₂(g) → H₂O(l) ; ΔH° = –285.8 kJ

Equation 3: C(graphite) + O₂(g) → CO₂(g) ; ΔH° = –393.5 kJ

Because of the way formation reactions are defined, any chemical reaction can be written as a combination of formation reactions, some going forward and some going back.

In this case, first, to obtain the enthalpy of the desired chemical reaction you need 2 moles of C(graphite) on reactant side and it is present in third equation. In this case it is necessary to multiply it by 2 to obtain the necessary amount. Since enthalpy is an extensive property, that is, it depends on the amount of matter present, since the equation is multiply by 2, the variation of enthalpy also.

Now, you need 3 moles of H₂(g) on reactant side and it is present in second equation. In this case it is necessary to multiply it by 3 to obtain the necessary amount and the variation of enthalpy also is multiplied by 3.

Finally, 1 mole of C₂H₆(g) must be a product and is present in the first equation. Since this equation has 1 mole of C₂H₆(g) on the reactant side, it is necessary to locate the C₂H₆(g) on the reactant side (invert it). When an equation is inverted, the sign of delta H also changes.

In summary, you know that three equations with their corresponding enthalpies are:

Equation 1: 2 CO₂(g) + 3 H₂O(l) → C₂H₆(g) + $\frac{7}{2}$ O₂(g); ΔH° = 1560 kJ

Equation 2: 3 H₂(g) + $\frac{3}{2}$ O₂(g) → 3 H₂O(l) ; ΔH° = –857.4 kJ