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3 years ago

Which of the following statements is true?

1 answer:

5 0

Answer: option D Chemical reaction rates vary with the conditions of the reaction, but nuclear decay rates do not.

Justification:

1) The rate of chemical reactions are affected by: concentration of the reactants, state of the reactants, temperature, and presence of catalizers. So the first part of the statement is true.

2) Nuclear decay rates are constant. The decay depends on the nature of the element but not the conditions. That is why dating fossils with radiactive isotopes is possible. So, the second part of the statement is true.

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Instant cold packs, often used to ice athletic injuries on the field, contain ammonium nitrate and water separated by a thin pla

RSB [31]

Answer: The enthalpy change of the reaction is -27. kJ/mol

Explanation:

To calculate the mass of water, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of water = 1 g/mL

Volume of water = 25.0 mL

Putting values in above equation, we get:

$1g/mL=\frac{\text{Mass of water}}{25.0mL}\\\\\text{Mass of water}=(1g/mL\times 25.0mL)=25g$

To calculate the heat released by the reaction, we use the equation:

$q=mc\Delta T$

where,

q = heat released

m = Total mass = [1.25 + 25] = 26.25 g

c = heat capacity of water = 4.18 J/g°C

$\Delta T$ = change in temperature = $T_2-T_1=(21.9-25.8)^oC=-3.9^oC$

Putting values in above equation, we get:

$q=26.25g\tiimes 4.18J/g^oC\times (-3.9^oC)=-427.9J=-0.428kJ$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of ammonium nitrate = 1.25 g

Molar mass of ammonium nitrate = 80 g/mol

Putting values in above equation, we get:

$\text{Moles of ammonium nitrate}=\frac{1.25g}{80g/mol}=0.0156mol$

To calculate the enthalpy change of the reaction, we use the equation:

$\Delta H_{rxn}=\frac{q}{n}$

where,

q = amount of heat released = -0.428 kJ

n = number of moles = 0.0156 moles

$\Delta H_{rxn}$ = enthalpy change of the reaction

Putting values in above equation, we get:

$\Delta H_{rxn}=\frac{-0.428kJ}{0.0156mol}=-27.44kJ/mol$

Hence, the enthalpy change of the reaction is -27. kJ/mol

4 0

3 years ago

Which of the following rules should you follow to balance chemical equations?

Firdavs [7]

Answer:

c. add coefficients as needed

Explanation:

A chemical equation is defined as the equation that shows changes in a chemical reaction. A chemical equation consist of reactant and product, reactant is at left side of the arrow and product is at right side of the arrow.

Reactant => Product

While balancing a chemical equation, the basic rule is to balance the coefficient as required. Coefficient represents the number of molecules and is used at front of a chemical symbol. Change in coefficient helps balance the number of atoms or molecules of the substances on both the sides of the arrow.

Subscripts are never allowed to change because it can change the chemical involved in the reaction.

Hence, the correct answer is "c. add coefficients as needed".

3 0

3 years ago

Ava, Inc., issued 7% bonds, dated January 1, with a face amount of $117,200 on January 1, 2016 for an issue price of 106.5. The

natta225 [31]

Complete Question

The complete question is shown on the first uploaded image

Answer:

10a The interest payment on the bond is = $ 8,204

10b The debit to cash for the bond proceeds is = $ 302,000

Explanation:

The explanation is shown on the second uploaded image

8 0

3 years ago

Define empirical formula and molecular formula with example of each

Arlecino [84]

Hi -----):):$/$:); wyd n

5 0

3 years ago

How do exothermic and endothermic differ

Ber [7]

Answer:

Explanation:

exothermic reactions involve release of heat whereas endothermic reaction involve absorption of heat.

6 0

2 years ago

Read 2 more answers