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3 years ago

Which units express heat capacity? J/°C, J/K, cal/°C, cal/K J/(gi°C), J/(giK), cal/(gi°C), cal/(giK) J, cal °C, K

Chemistry

2 answers:

11111nata11111 [884]3 years ago

7 0

Answer:

J/°C, J/K, cal/°C, cal/K

evablogger [386]3 years ago

3 0

Answer:

Explanation:

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Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°

miskamm [114]

Answer: The $\Delta H^o_{rxn}$ for the reaction is -1835 kJ.

Explanation:

Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.

According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.

The given chemical reaction follows:

$P_4(g)+10Cl_2(g)\rightarrow 4PCl_5(s)$ $\Delta H^o_{rxn}=?$

The intermediate balanced chemical reaction are:

(1) $PCl_5(s)\rightarrow PCl_3(g)+Cl_2(g)$ $\Delta H_1=157kJ$ ( × 4)

(2) $P_4(g)+6Cl_2(g)\rightarrow 4PCl_3(g)$ $\Delta H_2=-1207kJ$

The expression for enthalpy of the reaction follows:

$\Delta H^o_{rxn}=[4\times (-\Delta H_1)]+[1\times \Delta H_2]$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(4\times (-157))+(1\times (-1207))=-1835kJ$

Hence, the $\Delta H^o_{rxn}$ for the reaction is -1835 kJ.

6 0

3 years ago

Select each process that shows a physical change. Select all that apply.

erica [24]

Answer:

Chopping wood logs

A pot of water o a grate over a burning fire

Explanation:

Physical change is easily reversible. Burning/combustion is a chemical process where substances react rapidly with oxygen: this is usually irreversible.

The marshmallow, roasted food and burned wood all undergo combustion and hence are tagged chemical changes.

Explanation:

5 0

2 years ago

Read 2 more answers

Write down the group numbers for carbon,oxygen,nitrogen and sulphur

Bess [88]

Answer:

Carbon - 14

Oxygen - 16

Nitrogen - 15

Sulphur - 16

Explanation:

The question above is related to the "Periodic Table of Elements" which shows the proper arrangement of elements in a table. Every element falls on a group/family within the table. Each group has its own number, and the table has a total of 18 groups (from left to right). They are classified according to similarities in their characteristics. For example, group 1 is composed of alkali metals while group 2 is composed of alkali earth metals.

5 0

3 years ago

Which statements describe density? Check all that apply.

MrRa [10]

I think is 5 because you use density is found by mass divide by volume.

8 0

3 years ago

Read 2 more answers

For an alloy that consists of 78.2 g copper, 103.5 g zinc, and 2.8 g lead, what are the concentrations of (a) Cu, (b) Zn, and (c

TEA [102]

Answer:

Explanation:

Mass percent is defined as the mass of an element divided by the sum of masses of all the elements multiplied by 100. It is generally used to define the concentration. It does not depend on concentration.

It is given as;

Mass percent = (mass of an element / Total mass of the compound ) × 100

Mass of compound (alloy) = 78.2 g copper + 103.5 g zinc +2.8 g lead = 184.5 g

(a) Cu

Mass of Cu = 78.2

Mass percent = (78.2 / 184.5) * 100 = 42.38%

(a) Zn

Mass of Zn = 103.5

Mass percent = (103.5 / 184.5) * 100 = 56.10%

Mass of Pb = 2.8

Mass percent = (2.8 / 184.5) * 100 = 1.52%

8 0

3 years ago