isomorphism in étale cohomology

Question

Let $X$ be a proper $k$-variety with $k$ algebraically closed. Why is $H^2_{et}(X,\mathbf{Z}_\ell) \otimes_{\mathbf{Z}_\ell} (\mathbf{Q}_\ell/\mathbf{Z}_\ell) = (\mathbf{Q}_\ell/\mathbf{Z}_\ell)^{b_2(X) - \rho(X)}$, where $b_2(X) = \textrm{dim}_{\mathbf{Q}_\ell} H^2_{et}(X,\mathbf{Q}_\ell)$ and $\rho(X) = \mathrm{rk} \mathrm{NS}(X)$, rank of the Neron-Severi group of $X$ ?