An element has an atomic number of 78. the number of protons and electrons in a neutral atom of the element would be _____.

Chemistry

1 answer:

Maurinko [17]3 years ago

5 0

78 and 78. An atom of the element has 78 electrons and 78 protons.

The atomic number is 78, so the atom has 78 protons (+).

If the atom is neutral, it must contain 78 electrons (-).

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Read 2 more answers

Consider the following standard heats of formation:

cluponka [151]

Answer:

The Standard enthalpy of reaction: $\Delta H_{r}^{\circ } = -290\,kJ$

Explanation:

Given- Standard Heat of Formation:

$\Delta H_{f}^{\circ } [P_{4}O_{10}(s)]$ = -3110 kJ/mol,

$\Delta H_{f}^{\circ } [H_{2}O(l)]$ = -286 kJ/mol,

$\Delta H_{f}^{\circ } [H_{3}PO_{4}(s)]$ = -1279 kJ/mol

Given chemical reaction: P₄O₁₀(s) + 6H₂O → 4H₃PO₄

The standard enthalpy of reaction: $\Delta H_{r}^{\circ }$ = ?

To calculate the Standard enthalpy of reaction ( $\Delta H_{r}^{\circ }$ ), we use the equation:

$\Delta H_{r}^{\circ } = \sum \nu .\Delta H_{f}^{\circ }(products)-\sum \nu .\Delta H_{f}^{\circ }(reactants)$

$\Delta H_{r}^{\circ } = [4 \times \Delta H_{f}^{\circ } [H_{3}PO_{4}(s)]] - [1 \times \Delta H_{f}^{\circ } [P_{4}O_{10}(s)] + 6 \times \Delta H_{f}^{\circ } [H_{2}O(l)]]$