#whatsappchat a {
    position: fixed;
    z-index: 9999;
    float: right;
    cursor: pointer;
    min-width: 40px;
    max-width: 200px;
    text-align: center;
    -webkit-transition: All .5s ease;
    -moz-transition: All .5s ease;
    -o-transition: All .5s ease;
    -ms-transition: All .5s ease;
    transition: All .5s ease;
}

@media(max-width: 767px) {
    #whatsappchat a {
        max-width: 150px;
    }

    #whatsappchat .btn-web{
        display: none;
    }
}

@media(min-width: 768px) {
    #whatsappchat .btn-mobile{
        display: block;
    }
}